Device for detecting variation between cylinders of and device for detecting variation between banks of internal combustion engine

ABSTRACT

An inter-bank variation detection device of an internal combustion engine provided with a valve opening characteristic setting means ( 57 ) for changing the valve opening characteristic of an intake valve ( 9 ) for each of the cylinders (#1 to #4) or each of the bank (BL, BR); an indicator detecting means for detecting indicators of the state of combustion for each bank at the time of a first valve opening characteristic set by the valve opening characteristic setting means and the time of a second valve opening characteristic smaller than the first valve opening characteristic; a fuel injection amount variation detecting means ( 27 ) for detecting variation of the fuel injection amount for each bank by using the indicator (Xfn) detected by the indicator detecting means at the time of the first valve opening characteristic; and a valve opening characteristic variation detecting means ( 27 ) for detecting variation of the valve opening characteristic for each bank by using the indicator (Xsn) detected by the indicator detecting means at the time of the second valve opening characteristic and the variation of the fuel injection amount detected by the fuel injection amount variation detecting means is provided. It is also possible to change the valve opening characteristic of the intake valve by the valve opening characteristic setting means so that the variation of valve opening characteristic for each cylinder or each bank is eliminated.

TECHNICAL FIELD

The present invention relates to an inter-cylinder variation detectiondevice and an inter-bank variation detection device of an internalcombustion engine for detecting variation of valve openingcharacteristics, for example, the operating angle and/or amount of lift,and the variation of fuel injection amount among cylinders of aninternal combustion engine, particularly an internal combustion engineprovided with a valve opening characteristic setting means for changingthe amounts of air flowing into the cylinders.

BACKGROUND ART

In recent years, progress has been made in development of a valveopening characteristic control device making the valve openingcharacteristics, including the operating angle and/or amount of lift, ofintake valves provided in a plurality of cylinders variable so as tocontrol the amount of intake of an internal combustion engine. Forexample, the internal combustion engine disclosed in Japanese UnexaminedPatent Publication (Kokai) No. 2002-155779 sets the operating angleand/or amount of lift relatively small so as to reduce pump loss fromthat of a conventional internal combustion engine and, at the same time,improve the mileage.

Both in the above-mentioned internal combustion engine provided with avalve opening characteristic control device for changing the valveopening characteristics and in an internal combustion engine of theprior art, sometimes the operating angle and/or amount of lift amongcylinders deviates due to poor tuning or sometimes different amounts ofdeposits stick to the valves of the cylinders etc. Here, if setting theoperating angle and/or amount of lift relatively small by a valveopening characteristic control device in an internal combustion engineprovided with a valve opening characteristic control device, the amountof change to the intake air amount due to the poor tuning etc. becomestoo great to ignored and consequently sometimes exerts an adverseinfluence upon the drivability and emission. Accordingly, it isnecessary to correctly detect the variation of the valve openingcharacteristics, including the operating angle and/or amount of lift,among cylinders.

On the other hand, deviation of indicators of the state of combustionamong cylinders also includes variation of the fuel injection amount.For this reason, if not considering the inter-cylinder variation of thefuel injection amount, the variation of the valve openingcharacteristics, including the operating angle and/or amount of lift,cannot be correctly detected. Accordingly, if variation of the fuelinjection amount arises among cylinders, it is necessary to detect thevariation of the valve opening characteristics after correctly detectingthis variation of the fuel injection amount.

The present invention was made in consideration with such a circumstanceand has as an object thereof to provide an inter-cylinder variationdetection device and an inter-bank variation detection device of aninternal combustion engine able to detect the occurrence of variation ofthe valve opening characteristics and the variation of the fuelinjection amount among cylinders.

DISCLOSURE OF THE INVENTION

To attain the above object, according to a first aspect of theinvention, there is provided an inter-cylinder variation detectiondevice of an internal combustion engine provided with a valve openingcharacteristic setting means for changing an operating angle and/oramount of lift of an intake valve, wherein the valve openingcharacteristic setting means can set a first valve openingcharacteristic and a second valve opening characteristic having asmaller operating angle or amount of lift than that at the time of thefirst valve opening characteristic, and further provided with acalculating means for detecting an indicator of the state of combustionin each cylinder at the time of the first valve opening characteristicand the time of the second valve opening characteristic set by saidvalve opening characteristic setting means and, at the same time,calculating the deviation between these indicators and a standard valuefor each cylinder and a detecting means for detecting the variationamong cylinders by using the deviation for each cylinder at the time ofthe first valve opening characteristic and the deviation for eachcylinder at the time of the, second valve opening characteristiccalculated by said calculating means.

Namely, according to the first aspect of the invention, when detectingthe variation of the valve opening characteristic, not only thedeviation with respect to a standard value calculated at the time of thesecond valve opening characteristic, but also the deviation with respectto the standard value at the time of the first valve openingcharacteristic is calculated. In this way, it becomes possible tocorrectly detect the variation among cylinders by calculating thedeviation of each cylinder from indicators of the state of combustion attwo different valve opening characteristics and correcting it by usingthese deviations.

According to a second aspect of the invention, there is provided aninter-cylinder variation detection device of an internal combustionengine provided with a valve opening characteristic setting means forchanging an operating angle or amount of lift of an intake valve,wherein the valve opening characteristic setting means can set a firstvalve opening characteristic and a second valve opening characteristichaving a smaller operating angle or amount of lift than that at the timeof the first valve opening characteristic, and further provided with acalculating means for detecting an indicator of the state of combustionin each cylinder at the time of the first valve opening characteristicand the time of the second valve opening characteristic set by saidvalve opening characteristic setting means and, at the same time,calculating the deviation between these indicators and an average valueof the indicators of the state of combustion for the cylinders and adetecting means for detecting the variation among cylinders by using thedeviation for each cylinder at the time of the first valve openingcharacteristic and the deviation for each cylinder at the time of thesecond valve opening characteristic calculated by said calculatingmeans.

Namely, according to the second aspect of the invention, when detectingthe variation of the valve opening characteristic, not only thedeviation with respect to the average value among cylinders calculatedat the time of the second valve opening characteristic, but also thedeviation with respect to the average value among cylinders at the timeof the first valve opening characteristic is calculated. In this way, bycalculating the deviation of each cylinder from indicators of the stateof combustion in two different valve opening characteristics andcorrecting the variation by using these deviations, it becomes possibleto correctly detect the variation among cylinders.

According to a third aspect of the invention, there is provided thefirst or second aspect of the invention wherein the variation of thefuel injection amount is detected by the deviation for each cylinder atthe time of the first valve opening characteristic set by said valveopening characteristic setting means, and the variation of the valveopening characteristic is detected by the deviation for each cylinder atthe time of said second valve opening characteristic.

Namely, according to the third aspect of the invention, not only thevariation of the valve opening characteristic, but also occurrence ofvariation of the injection amount can be detected.

According to a fourth aspect of the invention, there is provided thethird aspect of the invention wherein when detecting the variation ofthe valve opening characteristic by the deviation for each cylinder atthe time of the second valve opening characteristic set by said valveopening characteristic setting means, the amount of variation of thefuel injection amount for each cylinder detected at the time of thefirst valve opening characteristic is corrected.

Namely, according to the fourth aspect of the invention, it becomespossible to correctly detect the variation of the valve openingcharacteristic after removal of the variation of the fuel injectionamount.

According to a fifth aspect of the invention, there is provided any ofthe first to fourth aspects of the invention wherein where detecting thevariation among cylinders by said detection device, control is performedso that the drive conditions at times of the first and second valveopening characteristics set by said valve opening characteristic settingmeans become the same.

Namely, in the fifth aspect of the invention, the indicators of thestate of combustion are made substantially the same so as to enablevariation to be corrected and detected more accurately by making thedrive conditions the same. Due to this, actions and effectssubstantially the same as those of the first to fourth aspects of theinvention can be obtained.

According to a sixth aspect of the invention, there is provided thefifth aspect of the invention wherein said drive conditions are therotational speed and torque.

Namely, according to the sixth aspect of the invention, actions andeffects substantially the same as those of the first to fifth aspects ofthe invention can be obtained.

According to a seventh aspect of the invention, there is provided thefifth or sixth aspect of the invention wherein said detection devicedetects the variation among cylinders in an idling state of the internalcombustion engine.

Namely, according to the seventh aspect of the invention, for thefrequency of detection and quality of the detection (fluctuation inrotation detected well), more desirably the variation is detected in theidling state. Due to this, actions and effects substantially the same asthose of the first to sixth aspects of the invention can be obtained.

According to an eighth aspect of the invention, there is provided thefirst or second aspect of the invention wherein said indicator of thestate of combustion includes at least one of an air/fuel ratio, rotationfluctuation, and combustion pressure of the internal combustion engine.

Namely, according to the eighth aspect of the invention, existence ofvariation of the valve opening characteristic and variation of the fuelinjection amount can be correctly detected by a relatively simpleconfiguration.

According to a ninth aspect of the invention, there is provided thefirst or second aspect of the invention wherein the valve openingcharacteristic of said intake valve is changed so that the variationamong cylinders detected by said detecting means is eliminated.

Namely, according to the ninth aspect of the invention, the valveopening characteristic is changed by exactly the amount of the variationof the valve opening characteristic among cylinders detected so as notto include the variation of the fuel injection amount, therefore moreprecise control becomes possible and it becomes possible to avoid theadverse influence upon the drivability and the emission by that.

According to a 10th aspect of the invention, there is provided aninter-cylinder variation detection device of an internal combustionengine provided with: a valve opening characteristic setting means forchanging a valve opening characteristic of an intake valve; an indicatordetecting means for detecting indicators of the state of combustion foreach cylinder at the time of a first valve opening characteristic and atthe time of a second valve opening characteristic smaller than the firstvalve opening characteristic set by the valve opening characteristicsetting means; a fuel injection amount variation detecting means fordetecting the variation of the fuel injection amount for each of thecylinders by using said indicator of the state of combustion detected bysaid indicator detecting means at the time of said first valve openingcharacteristic; and a valve opening characteristic variation detectingmeans for detecting variation of the valve opening characteristic foreach of said cylinders by using said indicator of the state ofcombustion detected by said indicator detecting means at the time ofsaid second valve opening characteristic and the variation of the fuelinjection amount detected by said fuel injection amount variationdetecting means.

Namely, according to the 10th aspect of the invention, the variation ofthe fuel injection amount for each cylinder is detected from theindicator of the state of combustion at the time of the first valveopening characteristic, and the variation of the fuel injection amountis not included from the indicator of the state of combustion at thetime of the second valve opening characteristic, so it becomes possibleto correctly detect the variation of the valve opening characteristicfor each cylinder.

According to an 11th aspect of the invention, there is provided the 10thaspect of the invention wherein said valve opening characteristicsetting means can change the valve opening characteristic of the intakevalve for each cylinder, and the variation of the valve openingcharacteristic for each of said cylinders detected by said valve openingcharacteristic variation detecting means is eliminated by the valveopening characteristic of said intake valve for each of said cylindersbeing changed by said valve opening characteristic setting means.

Namely, according to the 11th aspect of the invention, the valve openingcharacteristic is changed by exactly the amount of the variation of thevalve opening characteristic among cylinders detected so as not toinclude the variation of the fuel injection amount, therefore moreprecise control becomes possible, and it becomes possible to avoid anadverse influence upon the drivability and the emission by that.

According to a 12th aspect of the invention, there is provided the 10thor 11th aspect of the invention wherein said indicator of the state ofcombustion includes at least one of the air/fuel ratio, the rotationfluctuation, and the combustion pressure of the internal combustionengine.

Namely, according to the 12th aspect of the invention, the existence ofvariation of the valve opening characteristic and variation of the fuelinjection amount can be correctly detected by a relatively simpleconfiguration.

According to a 13th aspect of the invention, there is provided aninter-bank variation detection device of an internal combustion engineprovided with: a valve opening characteristic setting means for changinga valve opening characteristic of an intake valve for each bank; anindicator detecting means for detecting indicators of the state ofcombustion for each cylinder at the time of a first valve openingcharacteristic and at the time of a second valve opening characteristicsmaller than the first valve opening characteristic set by the valveopening characteristic setting means; a fuel injection amount variationdetecting means for detecting the variation of the fuel injection amountfor each of said cylinders by using said indicator of the state ofcombustion detected by said indicator detecting means at the time ofsaid first valve opening characteristic; and a valve openingcharacteristic variation detecting means for detecting the variation ofthe valve opening characteristic for each of said cylinders by usingsaid indicator of the state of combustion detected by said indicatordetecting means at the time of said second valve opening characteristicand the variation of the fuel injection amount detected by said fuelinjection amount variation detecting means and finding the average ofthe variations of the valve opening characteristics for the cylindersfor each bank to thereby detect the variation of the valve openingcharacteristic for each bank.

Namely, according to the 13th aspect of the invention, the variation ofthe fuel injection amount for each cylinder is detected from theindicator of the state of combustion at the time of the first valveopening characteristic, and the variation of the valve openingcharacteristic for each cylinder is detected from the indicator of thestate of combustion at the time of the second valve openingcharacteristic so as not to include the variation of the fuel injectionamount, therefore, by finding the average of the variations of the valveopening characteristics for the cylinders for each bank, it becomespossible to correctly detect the variation of the valve openingcharacteristic among banks.

According to a 14th aspect of the invention, there is provided aninter-bank variation detection device of an internal combustion engineprovided with: a valve opening characteristic setting means for changinga valve opening characteristic of an intake valve for each bank; anindicator detecting means for detecting indicators of the state ofcombustion for each bank at the time of a first valve openingcharacteristic and at the time of a second valve opening characteristicsmaller than the first valve opening characteristic set by the valveopening characteristic setting means; a fuel injection amount variationdetecting means for detecting the variation of the fuel injection amountfor each bank by using said indicator of the state of combustiondetected by said indicator detecting means at the time of said firstvalve opening characteristic; and a valve opening characteristicvariation detecting means for detecting the variation of the valveopening characteristic for each bank by using said indicator of thestate of combustion detected by said indicator detecting means at thetime of said second valve opening characteristic and the variation ofthe fuel injection amount detected by said fuel injection amountvariation detecting means.

Namely, according to the 14th aspect of the invention, the variation ofthe fuel injection amount for each bank is detected from the indicatorof the state of combustion at the time of the first valve openingcharacteristic, and the variation of the valve opening characteristicfor each bank is detected from the indicator of the state of combustionat the time of the second valve opening characteristic so as not toinclude the variation of the fuel injection amount, therefore, itbecomes possible to correctly detect the variation of the valve openingcharacteristic for each bank.

According to a 15th aspect of the invention, there is provided the 13thor 14th aspect of the invention wherein the valve opening characteristicof said intake valve for each bank is changed by said valve openingcharacteristic setting means so that the variation of the valve openingcharacteristic of each bank detected by said valve openingcharacteristic variation detecting means is eliminated.

Namely, according to the 15th aspect of the invention, the valve openingcharacteristic is changed by exactly the amount of the variation of thevalve opening characteristic among banks detected so as not to includethe variation of the fuel injection amount, therefore more precisecontrol becomes possible, and it becomes possible to avoid the adverseinfluence upon the drivability and the emission by that.

According to a 16th aspect of the invention, there is provided the 13thor 14th aspect of the invention wherein said indicator of the state ofcombustion includes at least one of the air/fuel ratio, the rotationfluctuation, and the combustion pressure of the internal combustionengine.

Namely, according to the 16th aspect of the invention, existence ofvariation of the valve opening characteristic and variation of the fuelinjection amount can be correctly detected by a relatively simpleconfiguration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a spark ignition type internal combustionengine having a valve opening characteristic control device of thepresent invention mounted thereon.

FIG. 2 is a schematic view of the configuration including an intakesystem etc. of the internal combustion engine shown in FIG. 1.

FIG. 3 is a perspective view of an intermediate drive mechanism.

FIG. 4 is an explanatory view of the schematic configuration of a valveopening characteristic control device.

FIG. 5 is a view of a flowchart of a program for operating aninter-cylinder variation detection device in the present invention.

FIG. 6 a is a view for explaining an example of an indicator of thestate of combustion in the present invention and shows a crank anglespeed.

FIG. 6 b is a view for explaining an example of an indicator of thestate of combustion in the present invention and shows the time requiredfor rotation by a crank angle of 90°.

FIG. 7 a is a view for explaining an example of an indicator of thestate of combustion in the present invention and shows an exhaustair/fuel ratio.

FIG. 7 b is a view for explaining an example of an indicator of thestate of combustion in the present invention and shows pressure in thecylinder.

FIG. 8 a is a view of a map of a predetermined value C1.

FIG. 8 b is a view of a map of a predetermined value C2.

FIG. 9 a is a view of an indicator Xfn at the time of a first valveopening characteristic.

FIG. 9 b is a view of an indicator Xsn at the time of a second valveopening characteristic.

FIG. 10 a is a view of an indicator Xfn at the time of the first valveopening characteristic in another case.

FIG. 10 b is a view of an indicator Xsn at the time of the second valveopening characteristic in another case.

FIG. 11 is a flowchart for explaining three further patterns when it isjudged as YES at step 102 of FIG. 5.

FIG. 12 a is a view of an indicator Xfn when the routine proceeds tostep 203 of FIG. 11.

FIG. 12 b is a view of an indicator Xsn when the routine proceeds tostep 203 of FIG. 11.

FIG. 12 c is a view of a new indicator Xsn′ when the routine proceeds tostep 203 of FIG. 11.

FIG. 13 a is a view of an indicator Xfn when the routine proceeds tostep 204 of FIG. 11.

FIG. 13 b is a view of an indicator Xsn when the routine proceeds tostep 204 of FIG. 11.

FIG. 13 c is a view of a new indicator Xsn′ when the routine proceeds tostep 204 of FIG. 11.

FIG. 14 a is a view of an indicator Xfn in a certain case when theroutine can proceed to step 205 of FIG. 11.

FIG. 14 b is a view of an indicator Xsn in a certain case when theroutine can proceed to step 205 of FIG. 11.

FIG. 14 c is a view of an indicator Xsn′ in a certain case when theroutine can proceed to step 205 of FIG. 11.

FIG. 15 is a lateral sectional view of an other spark-ignition typeinternal combustion engine having a valve opening characteristic controldevice of the present invention mounted thereon.

FIG. 16 is a vertical sectional view seen from the front surface of theinternal combustion engine shown in FIG. 15.

FIG. 17 is a view of a flowchart of a program for the operation of thevariation detection device among banks of the internal combustion engineshown in FIG. 15 and FIG. 16.

FIG. 18 a is a view for explaining the situation of finding a deviationΔXsL and a deviation ΔXsR.

FIG. 18 b is another view for explaining the situation of finding thedeviation ΔXsL and the deviation ΔXsR.

FIG. 19 is a view of another flowchart of a program for the operation ofthe variation detection device among banks of the internal combustionengine shown in FIG. 15 and FIG. 16.

FIG. 20 is a view of still another flowchart of a program for theoperation of the variation detection device among banks of the internalcombustion engine shown in FIG. 15 and FIG. 16.

FIG. 21 is a view of a flowchart of a program for the operationperformed for eliminating the variation among banks in the case of theinternal combustion engine shown in FIG. 15 and FIG. 16.

FIG. 22 is a view of a flowchart of a program for the operationperformed for eliminating the inter-cylinder variation in the case of afour-cylinder internal combustion engine where a valve openingcharacteristic control device is provided for each cylinder.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, an explanation will be given of embodiments of the presentinvention by referring to the attached drawings. In the followingdrawings, the same notations are attached to the same members. Forfacilitating understanding, these drawings are appropriately changed inscale of reduction.

FIG. 1 is a sectional view of a spark-ignition type internal combustionengine having an inter-cylinder variation detection device of thepresent invention mounted thereon, and FIG. 2 is a schematic view of theconfiguration including an intake system etc. of the internal combustionengine shown in FIG. 1. Note that the inter-cylinder variation detectiondevice of the present invention can also be mounted on an in-cylinderinjection type spark-ignition type internal combustion engine and acompression self ignition type diesel internal combustion engine.

Referring to FIG. 1 and FIG. 2, an engine body 1 is provided with acylinder block 2, a piston 3 reciprocally moving in this cylinder block2, and a cylinder head 4 attached onto the cylinder block 2. Further,the cylinder head 4 is provided with a spark plug 55. In the cylinderblock 2, as will be mentioned later, four cylinders 5 are formed. Ineach cylinder 5, a combustion chamber 6 defined by the cylinder block 2,the piston 3, and the cylinder head 4 is formed.

Each combustion chamber 6 is communicated to an intake port 7 and anexhaust port 8 formed in the cylinder head 4. An intake valve 9 isarranged between the combustion chamber 6 and the intake port 7. Theintake valve 9 opens or closes a flow passageway between the combustionchamber 6 and the intake port 7. On the other hand, an exhaust valve 10is arranged between the combustion chamber 6 and the exhaust port 8. Theexhaust valve 10 opens or closes the flow passageway between thecombustion chamber 6 and the exhaust port 8. The intake valve 9 islifted by an intake cam 13 via an intermediate drive mechanism 11 and arocker arm 12 mentioned later, and the exhaust valve 10 is lifted by anexhaust cam 15 via a rocker arm 14. The intake cam 13 is attached to anintake cam shaft 16, while the exhaust cam 15 is attached to an exhaustcam shaft 17.

An electronic control unit (ECU) 27 is configured by a microcomputerhaving a known configuration comprised of a read only memory (ROM), arandom access memory (RAM), a microprocessor (CPU), input ports, andoutput ports connected to each other by a bi-directional bus. The ECU 27has connected to it an air flow meter 19 and also various types ofsensors such as a load sensor 29 for generating an output voltageproportional to an amount of depression of an accelerator pedal(hereinafter referred to as an “accelerator depression amount”) and acrank angle sensor 30 for generating an output pulse whenever the crankshaft rotates by for example 30°. Further, it is connected to the sparkplug 55 and a fuel injection valve (not illustrated) and a throttlevalve 56 etc. and controls their operations. In the present embodiment,the opening degree of the throttle valve 56 can be changed regardless ofthe accelerator depression amount. By adjusting the opening degree ofthe throttle valve, the intake air pressure is controlled. Further, theECU 27 also transfers signals with a valve opening characteristiccontrol device 57 configured by including the intermediate drivemechanism 11 as will be mentioned later and controls the valve openingcharacteristic control device 57 and also controls the operating angleand the amount of lift as the valve opening characteristics of theintake valve 9. Note that, in FIG. 2, 52 indicates an intake pipe, and53 indicates a surge tank.

As shown in FIG. 2, the internal combustion engine 1 in the presentembodiment has four cylinders. As exhaust passageways thereof, first anexhaust passageway 41 from the first cylinder (#1) and an exhaustpassageway 44 from the fourth cylinder (#4) and an exhaust passageway 42from the second cylinder (#2) and an exhaust passageway 43 from thethird cylinder (#3) are combined to form two exhaust passageways 45 and46, then these are combined to form one exhaust passageway 47. Then, atthe portion where the exhaust passageway 41 from the first cylinder andthe exhaust passageway 44 from the fourth cylinder are combined, thatis, at one exhaust passageway 45 of the two exhaust passageways 45 and46, a first air/fuel ratio sensor 58 a is provided. In the same way asabove, at the portion where the exhaust passageway 42 from the secondcylinder and the exhaust passageway 43 from the third cylinder arecombined, that is, at one exhaust passageway 46 of the two exhaustpassageways 45 and 46, a second air/fuel ratio sensor 58 b is provided.These air/fuel ratio sensors 58 a and 58 b are connected to the ECU 27,whereby the information of the detected air/fuel ratios is supplied tothe ECU 27. Further, the portion 47 at which the exhaust passageways arecombined is provided with an exhaust purification device 59.

Next, referring to FIG. 3 and FIG. 4, an explanation will be given ofthe intermediate drive mechanism 11 and the valve opening characteristiccontrol device 57 configured including that. FIG. 3 is a perspectiveview of the intermediate drive mechanism 11, and FIG. 4 is anexplanatory view of the schematic configuration of the valve openingcharacteristic control device 57. Here, the intermediate drive mechanism11 has the same configuration as the intermediate drive mechanismdisclosed in Japanese Unexamined Patent Publication (Kokai) No.2001-263015 and is already known as a so-called “rocking cam mechanism”,so will be just simply explained below. The intermediate drive mechanism11 shown in FIG. 3 is provided for each cylinder of the internalcombustion engine. Accordingly, in the present embodiment, which is thecase of a four-cylinder internal combustion engine, four intermediatedrive mechanisms 11 are provided.

The intermediate drive mechanism 11 is provided with a cylindrical inputportion 21, a cylindrical first rocking cam 22 arranged at one side ofthe input portion 21 in an axial direction of this input portion 21, anda cylindrical second rocking cam 23 arranged at the opposite side to theabove one side of the input portion 21 in the axial direction of theinput portion 21. The input portion 21 and the rocking cams 22 and 23have cylindrical through holes extending in the axial direction centeredabout the axial lines thereof. A support pipe 24 passes through thesethrough holes. The input portion 21 and the rocking cams 22 and 23 aresupported by the support pipe 24 and can pivot about the support pipe24. The support pipe 24 is fixed to a cylinder head 4. Further, thesupport pipe 24 has a cylindrical through hole extending in the axialdirection centered about the axial line thereof. A control shaft 25passes through this through hole. The control shaft 25 can slide in theaxial direction of the support pipe 24 in the through hole of thesupport pipe 24.

Arms 21 a and 21 b are extended from the outer circumferential surfaceof the input portion 21 toward the diameter direction of the inputportion 21. A roller 21 c is arranged between front ends of these arms21 a and 21 b. The roller 21 c abuts against a cam surface 13 a of theintake cam 13 as shown in FIG. 1, so that the input portion 21 pivotsaround the support pipe 24 in accordance with the shape of the camsurface 13 a. On the other hand, from the outer circumferential surfacesof the rocking cams 22 and 23, noses 22 a and 23 a extend toward thediameter direction of the rocking cams 22 and 23. These noses 22 a and23 a can abut against the rocker arm 12.

Further, the input portion 21 and the rocking cams 22 and 23 and thecontrol shaft 25 are connected by a constant control mechanism (notillustrated). This control mechanism is configured so as to pivot theinput portion 21 and the rocking cams 22 and 23 in opposite directionsto each other when the control shaft 25 is relatively moved with respectto the support pipe 24. Especially, in the present embodiment, when thecontrol shaft 25 is moved in a direction D₁ with respect to the supportpipe 24, the input portion 21 and the rocking cams 22 and 23 pivot sothat the relative angles between the roller 21 c of the input portion 21and the noses 22 a and 23 a of the rocking cams 22 and 23 become large,while when the control shaft 25 is moved in a direction D₂ opposite tothe direction D₁ with respect to the support pipe 24, the input portion21 and the rocking cams 22 and 23 pivot so that relative angles betweenthe roller 21 c of the input portion 21 and the noses 22 a and 23 a ofthe rocking cams 22 and 23 become small. When the relative anglesbetween the roller 21 c and the noses 22 a and 23 a become large, thedistances between the roller 21 c and the noses 22 a and 23 a becomelong, while conversely when the relative angles between the roller 21 cand the noses 22 a and 23 a become small, the distances between theroller 21 c and the noses 22 a and 23 a become short.

On the other hand, as seen from FIG. 1, the amount of the lift of theintake valve 9 by the intake cam 13 changes according to the distancesbetween the roller 21 c and the noses 22 a and 23 a. Namely, if thedistances between the roller 21 c and the noses 22 a and 23 a becomelong, when the roller 21 c abuts against a peak 13 b of the intake cam13, the period where the noses 22 a and 23 a lift the intake valve 9becomes long and, at the same time, the amount of lift becomes large.Conversely, if the distances between the roller 21 c and the noses 22 aand 23 a become short, when the roller 21 c abuts against the peak 13 bof the intake cam 13, the period where the noses 22 a and 23 a lift theintake valve 9 becomes short and, at the same time, the amount of liftbecomes small. Namely, when the distances between the roller 21 c andthe noses 22 a and 23 a become long, the operating angle of the intakevalve 9 becomes large and, at the same time, the amount of lift of theintake valve 9 becomes large, while when the distances between theroller 21 c and the noses 22 a and 23 a become short, the operatingangle of the intake valve 9 becomes small and, at the same time, theamount of lift of the intake valve 9 becomes small.

Accordingly, in the intermediate drive mechanism 11, when the controlshaft 25 is moved in the first direction D₁, the operating angle of theintake valve 9 becomes large and, at the same time, the amount of liftof the intake valve 9 becomes large, while when the control shaft 25 ismoved in the second direction D₂, the operating angle of the intakevalve 9 becomes small and, at the same time, the amount of lift of theintake valve 9 becomes small. Note that, in the present embodiment, theoperating angle and the amount of lift used as the valve openingcharacteristics have constant relationships in this way, but in otherembodiments, it is also possible even if only the operating angle oronly the amount of lift is changed as the valve opening characteristic.

As mentioned above, the present embodiment relates to the case of afour-cylinder internal combustion engine, so has four of theintermediate drive mechanisms 11. The four intermediate drive mechanisms11 are arranged in series as shown in FIG. 4. All of the intermediatedrive mechanisms 11 are provided on one support pipe 24 and one controlshaft 25. Accordingly, when the valve opening characteristic controldevice 57 normally operates, the same valve opening characteristics canbe obtained in all cylinders.

As shown in FIG. 4, an electric actuator 26 is connected to one endportion of the control shaft 25. The position of the control shaft 25can be controlled by this actuator 26. This electric actuator 26 isconnected to the ECU 27 and controlled by this. That is, in the presentembodiment, the electric actuator 26 can be controlled by the ECU 27 soas to move the position of the control shaft 25 in the axial directionthereof. The distances between the roller 21 c and the noses 22 a and 23a are changed by this, thus the operating angle and amount of lift usedas the valve opening characteristics of the intake valve 9 can becontinuously controlled.

In the vicinity of the other end portion of the control shaft 25, aposition sensor 28 for detecting the position of the control shaft 25 inthe axial direction is arranged. The position of the control shaft 25can be detected by this position sensor 28. This position sensor 28 isconnected to the ECU 27, whereby the information of the position of thecontrol shaft 25 detected by the position sensor 28 is supplied to theECU 27. Note that, as mentioned above, in the present embodiment, thedistances between the roller 21 c and the noses 22 a and 23 a arechanged by controlling the position of the control shaft 25, and theoperating angle and the amount of lift used as the valve openingcharacteristics of the intake valve 9 are controlled by this, thereforeit can be said that the position sensor 28 is a valve openingcharacteristic sensor detecting the valve opening characteristic.

In the internal combustion engine of the present embodiment, in theconfiguration described above, various types of control such as fuelinjection amount control, ignition timing control, and intake amountcontrol are executed by the ECU 27 based on signals from varioussensors. Especially, the intake amount control is carried out by the ECU27 controlling both of the valve opening characteristic control device57 and the throttle valve 56 in more detail. Namely, in the presentembodiment, the operating angle and the amount of lift used as the valveopening characteristics of the intake valve 9 can be continuouslycontrolled by the valve opening characteristic control device 57, andthe intake pressure can be controlled by the throttle valve 56,therefore usually the intake amount is controlled by jointly controllingthe valve opening characteristics (amount of lift and operating angle)and the intake pressure.

FIG. 5 is a view of a flowchart of a program for the operation of theinter-cylinder variation detection device of the internal combustionengine in the present invention. A program 100 shown in FIG. 5 isexecuted by the ECU 27 in the case of normal operation where the intakeamount becomes constant, for example, at the time of idling afterwarmup. At step 101 of the program 100, the indicator of the state ofcombustion when the valve opening characteristic is set a first valveopening characteristic (hereinafter referred to as “the first valveopening characteristic”), that is, an indicator fluctuating in relationto the state of combustion (hereinafter referred to as the “indicator ofthe state of combustion” or the “indicator”) Xfn, is detected for eachcylinder (hereinafter, the indicator of the state of combustion of thefirst cylinder at the first valve opening characteristic will beindicated as “Xf1”, and indicators of the second, third, and fourthcylinders will be indicated as “Xf2”, “Xf3”, and “Xf4” and, further,where these are indicated together, indicated as “Xfn”). For this firstvalve opening characteristic, the case where the operating angle and/oramount of lift is relatively large and the variation of the valveopening characteristics is small enough to ignore is selected.Accordingly, at the time of the first valve opening characteristic, theintake amount becomes relatively large. Note that the case of anembodiment controlling only one of the operating angle and amount oflift by the valve opening characteristic control device is made a casewhere the operating angle or amount of lift is relatively large.

Here, an explanation will be given of the indicator of the state ofcombustion. FIG. 6 a and FIG. 6 b and FIG. 7 a and FIG. 7 b are viewsfor explaining examples of the indicator of the state of combustion inthe present invention. In these drawings, the fluctuation of the enginespeed, the time required for the rotation by a crank angle of 90°(hereinafter referred to as “T90”), the exhaust air/fuel ratio(hereinafter appropriately referred to as “A/F”), and the cylinderpressure are shown.

First, an explanation will be given of the case where the fluctuation ofthe engine speed is made the indicator of the state of combustion asshown in FIG. 6 a. For the fluctuation of the engine speed, the changeof the engine speed along with time is found based on the signal fromthe crank angle sensor 30. Therefore, by analyzing this by therelationship with the crank angle, the fluctuation of the rotation speedcorresponding to the explosion in each cylinder (for example thedifference between the rotational speed of the engine immediately beforethe ignition in each cylinder and the peak rotational speed after theignition) can be found. Then, this value can be used as the fluctuationof the engine speed corresponding to each cylinder. In FIG. 6 a, anordinate indicates the crank angle speed, and an abscissan indicates thecrank angle from top dead center TDC. A solid line YA0 shown in FIG. 6 aindicates the crank angle speed at the time of normal operation, whilethe two dotted lines YA1 and YA2 indicate crank angle speeds where thecrank angle is deviated to the retarded side and advanced side from thatat the time of normal operation. As shown in FIG. 6 a, the displacementsof the crank angle speed from top dead center TDC to 90° of the solidline YA0 and the dotted lines YA1 and YA2 are indicated as the enginespeed fluctuations XA0, XA1, and XA2. Here, XA0 corresponds to thestandard value X mentioned later. Further, the difference between theengine speed fluctuation XA0 at the time of normal operation and theengine speed fluctuation XA1 when the crank angle is at the retardedside is indicated by ΔXA1, and the difference between the engine speedfluctuation XA0 at the time of normal operation and the engine speedfluctuation XA2 when the crank angle is at the advanced side isindicated by ΔXA2. When the fluctuation of the engine speed is employedas the indicator of the state of combustion, the indicator Xfn at step101 of FIG. 5 corresponds to XA1 and XA2 in FIG. 6 a. Further, theindicator Xsn where the valve opening characteristic at step 104mentioned later is changed also corresponds to XA1 and XA2 in FIG. 6 a.

In the same way as above, as shown in FIG. 6 b, an explanation will begiven of the case where the time T90 required for rotation by a crankangle of 90° is employed as the indicator of the state of combustion.The T90 is calculated at the ECU 27 from the crank angles obtained bythe crank angle sensor 30 shown in FIG. 2. In FIG. 6 b, the ordinateindicates the position of the piston 3. The top dead center TDC and thebottom dead center BDC are indicated by one-dot-chain lines. Theabscissa of FIG. 6 b indicates the time from the top dead center TDC.The solid line YB0 shown in FIG. 6 b indicates the position of thepiston 3 at normal operation, while the two dotted lines YB1 and YB2indicate positions of the piston 3 when it is deviated to the retardedside and the advanced side from the time of normal operation. In FIG. 6b, at the center between the top dead center TDC and the bottom deadcenter BDC, the position of the piston 3 at the crank angle 90° from thetop dead center TDC is indicated by the dotted line. As shown in FIG. 6b, the displacements T90 from the top dead center TDC to 90° of thesolid line YB0 and the dotted lines YB1 and YB2 are indicated by XB0,XB1, and XB2. Here, XB0 corresponds to the standard value X mentionedlater. Further, the difference between the displacement XB0 at the timeof normal operation and XB1 of T90 at the retarded side is indicated byΔXB1, and the difference between the displacement XB0 at the time ofnormal operation and XB2 of T90 at the advanced side is indicated byΔXB2. FIG. 6 b shows T90 as the time required for rotation by a crankangle of 90°, but cases where the times T120, T180, T360, etc. requiredfor rotation by a crank angle of 120°, 180°, 360°, etc. are employed arealso deemed to be included within the scope of the present invention.When T90 is employed as the indicator of the state of combustion, theindicator Xfn at step 101 of FIG. 5 corresponds to XB1 and XB2 in FIG. 6b. Further, the indicator Xsn where the valve opening characteristic atstep 104 mentioned later is changed also corresponds to XB1 and XB2 inFIG. 6 b.

Next, an explanation will be given of the case where the air/fuel ratioA/F is employed as the indicator of the state of combustion by usingFIG. 7 a. For the air/fuel ratio, in the present embodiment, twoair/fuel ratio sensors 58 a and 58 b are provided in the exhaust systemas mentioned above, therefore the air/fuel ratio in each cylinder can befound by analyzing the change along with time of the air/fuel ratiodetected by them by the relationship with the crank angle. Note that, itis also possible to provide air/fuel ratio sensors in the exhaustpassageways 41, 42, 43, and 44 for each cylinder and find the air/fuelratio for each cylinder by those. In FIG. 7 a, the ordinate indicatesthe air/fuel ratio A/F, and the abscissa indicates the crank angle. Asolid line YC0 shown in FIG. 7 a indicates the air/fuel ratio A/F innormal operation, while the two dotted lines YC1 and YC2 indicate theair/fuel ratios A/F when deviated to the lean side and rich side fromthe time of normal operation. As shown in FIG. 7 a, the air/fuel ratiosA/F at certain crank angles of the solid line YC0 and the dotted linesYC1 and YC2 are indicated by XC0, XC1, and XC2. Here, XC0 corresponds tothe standard value X mentioned later. Further, the difference betweenthe air/fuel ratio XC0 at the time of normal operation and the air/fuelratio XC1 when at the rich side is indicated by ΔXC1, and the differencebetween the air/fuel ratio XC0 at the time of normal operation and theair/fuel ratio XC2 when at the lean side is indicated by ΔXC2. When theair/fuel ratio is employed as the indicator of the state of combustion,the indicator Xfn at step 101 of FIG. 5 corresponds to XC1 and XC2 inFIG. 7 a. Further, the indicator Xsn where the valve openingcharacteristic at step 104 mentioned later is changed also correspondsto XC1 and XC2 shown in FIG. 7 a.

In the same way as above, an explanation will be given of the case wherethe cylinder pressure is employed as the indicator of the state ofcombustion by using FIG. 7 b. In FIG. 7 b, the ordinate indicates thecylinder pressure, and the abscissa indicates the crank angle. The solidline YD0 shown in FIG. 7 b indicates the cylinder pressure at normaloperation, while the two dotted lines YD1 and YD2 indicate the cylinderpressures where deviated from that at the time of normal operation tothe high pressure side and the low pressure side. As shown in FIG. 7 b,the cylinder pressures where the maximum pressures (combustionpressures) are given in the cylinders at the solid line YD0 and thedotted lines YD1 and YD2 are indicated by XD0, XD1, and XD2. Here, XD0corresponds to the standard value X mentioned later. Further, thedifference between the cylinder pressure XD0 at the time of normaloperation and the cylinder pressure XD1 when at the high pressure sideis indicated by ΔXD1, and the difference between the cylinder pressureXD0 at the time of normal operation and the cylinder pressure XD2 whenat the low pressure side is indicated by ΔXD2. When the cylinderpressure is employed as the indicator of the state of combustion, theindicator Xfn at step 101 of FIG. 5 corresponds to XD1 and XD2 in FIG. 7b. Further, the indicator Xsn at step 104 mentioned later alsocorresponds to XD1 and XD2 in FIG. 7 b when the valve openingcharacteristic is changed.

In this way, in the present invention, as the indicator of the state ofcombustion, the fluctuation of the engine speed, T90, air/fuel ratio,and cylinder pressure (combustion pressure) can be employed. By this,the existence of variation of the valve opening characteristic can becorrectly detected with a relatively simple configuration as will bementioned later. Further, it is also possible to simultaneously detect aplurality of indicators among them and use them as indicators of thestate of combustion.

When the indicator Xfn of the state of combustion as described above atthe first valve opening characteristic is detected for each cylinder atstep 101 shown in FIG. 5, the routine proceeds to step 102. At step 102,an absolute value of the difference between the indicator Xfn obtainedat step 101 and the standard value Xfr previously determined for theindicator (in more detail, the magnitude of the difference from thepreviously determined standard value) is calculated, and it is judgedwhether or not this absolute value of the difference is larger than apredetermined value C1. This standard value Xfr is a normal value ortarget value in each drive state for the indicator of the state ofcombustion found in advance by experiments etc., formed into a map, andstored in the ECU 27. Namely, the system is configured so that thestandard value Xfr of the indicator of the state of combustion at thattime is obtained from for example the engine speed and the openingdegree of the accelerator. Further, the predetermined value C1 at step101 is a value larger than zero. FIG. 8 a is a view of a map of thepredetermined value C1. As shown in FIG. 8 a, the predetermined value C1is stored in the ECU 27 in the form of a map as a function of the load Land the engine speed N. Other measurement values mentioned later areformed into maps and stored in the ECU 27 in the same way as above. Inthe ECU 27, when it is judged that the absolute value of the differencebetween the indicator Xfn and the standard value Xfr (|Xfn−Xfr|) islarger than the predetermined value C1, the routine proceeds to step103, while when it is judged that the absolute value of this difference(|Xfn−Xfr|) is smaller than the predetermined value C1, the routineproceeds to step 104. Note that the predetermined standard value Xfr maybe an average value Xfavg (=ΣXfn/n) from the indicator Xf1 to Xf4 aswell.

At step 103, the difference between the indicator Xfn obtained at step101 and the standard value Xfr previously determined for the indicator(in more detail, the magnitude of the difference from the previouslydetermined standard value) ΔXfn is calculated for each cylinder. Thisstandard value Xfr is the normal value or the target value in each drivestate for the indicator of the state of combustion. It is found inadvance by experiments etc., formed into a map, and stored in the ECU27. Namely, the system is configured so that the standard value Xfr ofthe indicator of the state of combustion is obtained from for examplethe engine speed and the opening degree of the accelerator. By step 103,the differences ΔXfn (that is, the deviation for each cylinder) betweenthe indicators Xfn of the states of combustion of the cylinders (firstto fourth cylinders) and the standard value Xfr (that is, ΔXf1=Xf1−XFr,ΔXf2=Xf2−Xfr, ΔXf3=Xf3−Xfr, ΔXf4=Xf4−Xfr) are obtained. The indicatorXfn at the time of the first valve opening characteristic represents theinfluence of the variation of the fuel injection amount as will bementioned later, therefore, by calculating the deviation ΔXfn from thestandard value Xfr, the variation of the fuel injection amount islearned.

In the present embodiment, in FIG. 6 a to FIG. 7 b, the value at thetime of normal operation, for example, XA0, corresponds to the standardvalue Xfr. Further, the difference, for example, ΔXA1 between this XA0and the value in each cylinder, for example XA1, is calculated as thedeviation ΔXfn. Accordingly, ΔXA1 and ΔXA2 in FIG. 6 a correspond to thedeviation ΔXfn at step 103. In the same way as above, ΔXB1 and ΔXB2 inFIG. 6 b, ΔXC1 and ΔXC2 in FIG. 7 a, and ΔXD1 and ΔXD2 in FIG. 7 bcorrespond to the deviation ΔXfn. Further, in FIG. 6 a, FIG. 6 b, FIG. 7a, and FIG. 7 b, only two cylinders are shown, but in actuality, thesame deviation is calculated also for the other cylinders, for example,in the case of four cylinders, the remaining two cylinders. Note that,in other embodiments, it is also possible to calculate an average valueXfavg (=ΣXfn/n) of the indicators Xfn obtained with respect to thecylinders and use the deviation between the average value Xfavg and eachindicator Xfn (=Xfavg−Xfn) as the deviation ΔXfn or ΔXsn mentionedlater.

Next, at step 104, the indicator Xsn of the state of combustion when thevalve opening characteristic is made the second valve openingcharacteristic is detected for each cylinder. This is a control stepsimilar to step 101 of the control routine of FIG. 5. In the control bythe present control routine as well, at this second valve openingcharacteristic, the operating angle and/or amount of lift is madesmaller than that at the time the first valve opening characteristic.Accordingly, at the time of the second valve opening characteristic, theintake amount becomes relatively small. Note that, in the case of anembodiment where only one of the operating angle and amount of lift iscontrolled by the valve opening characteristic control device, theamount of lift is made smaller than that at the time of the first valveopening characteristic.

Further, the intake amount and the rotation speed and the engine loadwhen the valve opening characteristic is made the second valve openingcharacteristic at step 104 are made the same as those at the time whenthe valve opening characteristic was the first valve openingcharacteristic at step 101. Namely, if the valve opening characteristiccontrol device 57 normally operates, the throttle valve 56 is controlledso that the intake amounts become the same at the time of the valveopening characteristics. Note that, naturally, the indicator Xsn of thestate of combustion detected at step 104 is made the same type as theindicator Xfn of the state of combustion detected at step 101.

When the indicator Xsn of the state of combustion at the second valveopening characteristic is detected for each cylinder at step 104, theroutine proceeds to step 105. At step 105, the difference (Xfn−Xfr)between the indicator Xfn and the standard value Xfr is found, then itis judged whether or not the absolute value of this difference |Xfn−Xfr|is larger than a predetermined value C1′. The predetermined value C1′ atstep 105 is a value larger than zero. In the same way as the case of thepredetermined value C1 mentioned above, the predetermined value C1′ isstored in the ECU 27 in the form of a map as a function of the load Land the engine speed N. Note that when the routine passes step 103, itis also possible to directly use the absolute value of the deviationΔXfn. When it is judged at step 105 that the absolute value |Xfn−Xfr| islarger than the predetermined value C1′, the routine proceeds to step106, while when it is judged that the absolute value |Xfn−Xfr| is notlarger than the predetermined value C1′, the routine proceeds to step107.

Here, an explanation will be given of the above judgment at step 105.When there is variation in the valve opening characteristic controldevice 57, that is, when there is variation in the valve openingcharacteristics, a difference occurs in the intake amount amongcylinders. It is learned that the smaller the operating angle and amountof lift, the larger the influence thereof. On the other hand, the largerthe operating angle and amount of lift, the smaller the influence uponthe indicator due to the variation of the valve opening characteristics.Further, when the operating angle and the amount of lift are certainextents of value or more, it can be considered that the influence of thevariation of the valve opening characteristics can be substantiallyignored. For this reason, when the operating angle and amount of liftare relatively large, that is, when the influence with respect to theabove indicator is detected at the time of the first valve openingcharacteristic, it can be judged that this cause is not variation of thevalve opening characteristic control device 57, but due to a portionother than the valve opening characteristic control device 57, i.e., inthe present invention, the variation of the fuel injection amount by thefuel injection system. Namely, when the absolute value |Xfn−Xfr| of thedifference (Xfn−Xfr) between the indicator Xfn and the standard valueXfr is larger than a predetermined value C1′ as at step 105, it can bejudged that variation of the fuel injection amount had occurred. On theother hand, when the operating angle and the amount of lift arerelatively small, that is, when the influence with respect to the aboveindicator occurs at the time of the second valve opening characteristic,this cause is not only the occurrence of variation of the valve openingcharacteristic by the valve opening characteristic control device 57,but also the intermixture of variation of the fuel injection amount bythe fuel injection system which is a portion other than the valveopening characteristic control device 57.

Then, when the absolute value |Xfn−Xfr| of the difference (Xfn−Xfr)between the indicator Xfn and the standard value Xfr is larger than thepredetermined value C1′, the routine proceeds to step 106. At step 106,by subtracting the difference (Xfn−Xfr) between the indicator Xfn andthe standard value Xfr from the indicator Xsn at the time of the secondvalve opening characteristic calculated at step 104, a new indicatorXsn′ (=Xsn−(Xfn−Xfr)) for the second valve opening characteristic iscalculated for each cylinder. For example, when the internal combustionengine is a four-cylinder type, four new indicators fromXs1′(=Xs1−(Xf1−Xfr)) to Xs4′(=Xs4−(Xf4−Xfr)) are calculated. Here, thedifference (Xfn−Xfr) is not an absolute value, but in a state includingpositive and negative signs as it is. Accordingly, when the difference(Xfn−Xfr) is a positive value, the new indicator Xsn′ becomes smallerthan the original indicator Xsn, while when the difference (Xfn−Xfr) isa negative value, the new indicator Xsn′ becomes larger than theoriginal indicator Xsn. In this way, by correcting the amount ofvariation of the fuel injection amount (Xfn−Xfr=ΔXfn), a new indicatorXsn′ not including the influence of the variation of the fuel injectionamount can be calculated. Accordingly, the new indicator Xsn′ willrepresent the influence by only the variation of the valve openingcharacteristic.

Next, at step 107, the absolute value of the difference between theindicator Xsn obtained at step 104 or the new indicator Xsn′ obtained atstep 106 and the standard value Xsr previously determined for theseindicators (in more detail, the magnitude of the difference from thepreviously determined standard value) is calculated. Namely, when thenew indicator Xsn′ is not calculated (where NO is judged at step 105),the absolute value (|Xsn−Xsr|) of the difference between the indicatorXsn (Xs1 to Xs4 in the case of four cylinders) and the standard valueXsn is calculated. Then, where the new indicator Xsn′ was calculated foreach cylinder at step 106, the absolute value (|Xsn′−Xsr|) of thedifference between the new indicator Xsn′ (Xs1′ to Xs4′ in the case offour cylinders) and the standard value Xsn is calculated. This standardvalue Xsr is the normal value or target value for the indicator in eachdrive state in the same way as the standard value Xfr. Further, at step107, it is judged whether or not the absolute value (|Xsn−Xsr| or|Xsn′−Xsr|) of these differences is larger than a predetermined valueC2. The predetermined value C2 in the above step 107 is a value largerthan zero. FIG. 8 b is a view of a map of the predetermined value C2. Asshown in FIG. 8 b, the predetermined value C2 is stored in the ECU 27 inthe form of a map as a function of the load L and the engine speed N.When it is judged at step 107 that the absolute value (|Xsn−Xsr| or|Xsn′−Xsr|) of the difference is larger than the predetermined value C2,the routine proceeds to step 108. On the other hand, when it is judgedat step 107 that the absolute value of the difference mentioned above isnot larger than the predetermined value, it is judged that there is novariation of the valve opening characteristic and the processing isended. Note that, the predetermined standard value Xsr may be theaverage value Xsavg (=ΣXsn/n) from the indicators Xs1 to Xs4 as well.

At step 108, the difference ΔXsr between the indicator Xsn obtained atstep 104 or the new indicator Xsn′ obtained at step 106 and the standardvalue Xsr previously determined for these indicators (in more detail,the magnitude of the difference from the previously determined standardvalue) is calculated for each cylinder. This standard value Xsr is thenormal value or target value for the indicator in each drive state inthe same way as the above standard value Xfr. For example, if therelationship shown in FIG. 6 a for the time of the second valve openingcharacteristic different from the case of the first valve openingcharacteristic mentioned above is obtained, the value at the time ofnormal operation, for example, XA0, corresponds to the standard valueXsr. Then, the difference, for example ΔXAL between this XA0 and thevalue in each cylinder, for example XA1, is calculated as the deviationΔXsn. Accordingly, in this case, ΔXAL and ΔXA2 in FIG. 6 a correspond tothe deviation ΔXsn at step 108. In the same way as the above mentionedcase, also ΔXB1 and ΔXB2 in FIG. 6 b, ΔXC1 and ΔXC2 in FIG. 7 a, andΔXD1 and ΔXD2 in FIG. 7 b can correspond to the deviation ΔXsn. By step108, the differences ΔXsn (that is, ΔXs1=Xs1−Xsr, ΔXs2=Xs2−Xsr,ΔXs3=Xs3−Xsr, and ΔXs4=Xs4−Xsr, or ΔXs1=Xs1′−Xsr, ΔXs2=Xs2′−Xsr,ΔXs3=Xs3′−Xsr, and ΔXs4=Xs4′−Xsr) between indicators Xsn of the state ofcombustion of cylinders (first to fourth cylinders) or the new indicatorXsn′ and the standard value Xsr (that is, the deviation for cylinder) isobtained, and the processing is ended. As mentioned above, in theindicator Xsn at the time of the second valve opening characteristic,the variation of the fuel injection amount and the variation of thevalve opening characteristic can be mixed, but in the present invention,where there is variation of the fuel injection amount, this is corrected(the difference (Xfn−Xfr) is subtracted from the indicator Xsn),therefore, by calculating the deviation ΔXsn from the standard valueXsr, just the variation of the valve opening characteristic can becalculated.

FIG. 9 a is a view of an indicator Xfn at the time of the first valveopening characteristic in any cylinder #1 and cylinder #2 in theinternal combustion engine provided with four cylinders (#1 to #4) as anexample. Further, FIG. 9 b is a view of an indicator Xsn at the time ofthe second valve opening characteristic in any cylinder #1 and #2.Dotted lines X shown in these diagrams indicate standard values andcorrespond to XA0 in FIG. 6 a, XB0 in FIG. 6 b, XC0 in FIG. 7 a, and XD0in FIG. 7 b. As shown in FIG. 9 a, when the indicators Xfn at the timeof the first valve opening characteristic in the cylinder #1 and thecylinder #2 are approximately equal or they are slightly deviated to anextent that does not exceed a predetermined value C1 although notillustrated, it is judged at step 102 of FIG. 5 that the absolute value(|Xfn−Xfr|) of the difference between the indicator Xfn and the standardvalue Xfr is not larger than the predetermined value C1 (NO judgment).Accordingly, in this case, the routine will proceed to step 104 withoutpassing through step 103. Further, when the absolute value |Xfn−Xfr| ofthe difference (Xfn−Xfr) between the indicator Xfn and the standardvalue Xfr is not larger than the predetermined value C1′, the amount ofvariation of the fuel injection amount is not corrected at step 106.Namely, it is judged that variation of the fuel injection amount doesnot occur. Further, as shown in FIG. 9 b, when indicators Xsn at thetime of the second valve opening characteristic in the cylinder #1 andthe cylinder #2 are approximately equal or they are slightly deviated toan extent that does not exceed a predetermined value C2 although notillustrated, it is judged at step 107 that the absolute value(|Xsn−Xsr|) of the difference between the indicator Xsn and the standardvalue Xsr is not larger than the predetermined value C2 (NO judgment).That is, in this case, it is also judged that variation of the valveopening characteristic does not occur.

FIG. 10 a and FIG. 10 b are views the same as FIG. 9 a and FIG. 9 bshowing indicators Xsn at times of the first valve openingcharacteristic and second valve opening characteristic in any cylinders#1 and #2 in other cases. The dotted lines X are as mentioned before. Asshown in FIG. 10 a, when the indicators Xfn at the time of the firstvalve opening characteristic in the cylinder #1 and the cylinder #2 areapproximately equal or they are slightly deviated to an extent that doesnot exceed a predetermined value C1 although not illustrated, asmentioned above, it is judged NO at step 102 and the routine proceeds tostep 104. Further, when the absolute value |Xfn−Xfr| of the difference(Xfn−Xfr) between the indicator Xfn and the standard value Xfr is notlarger than the predetermined value C1′, the amount of variation of thefuel injection amount is not corrected at step 106. Namely, it is judgedthat variation of the fuel injection amount does not occur. On the otherhand, for the indicator Xsn at the time of the second valve openingcharacteristic, as shown in FIG. 10 b, indicators Xs1 and Xs2 aredeviated from the standard line X in opposite directions to each other.In such a case, at step 107 of the program 100 shown in FIG. 5, it maybe judged that the absolute value (|Xsn−Xsr|) of the difference betweenthe indicator Xsn and the standard value Xsr is larger than apredetermined value C2 (YES judgment). Then, at step 108, the deviationΔXsn (ΔXs1 and ΔXs2) is calculated. That is, in this case, it is judgedthat only variation of the valve opening characteristic occurs.

At step 102 of the program 100 of FIG. 5, when it is judged that theabsolute value (|Xfn−Xfr|) of the difference between the indicator Xfnat the time of the first valve opening characteristic and the standardvalue Xfr is larger than the predetermined value C1 (YES judgment), thepatterns can be classified to at least three types. FIG. 11 is aflowchart for explaining further the three patterns when it is judgedYES at step 102 of FIG. 5. Accordingly, an explanation will be given ofthese three patterns by referring to FIG. 11.

First, at step 201 shown in FIG. 11, it is judged whether or not thepositive and negative signs of the deviation ΔXfn calculated at step 103of FIG. 5 and the positive and negative signs of the deviation ΔXsncalculated at step 108 are equal. When the signs of these deviation ΔXfnand deviation ΔXsn are equal, the routine proceeds to step 202. At step202, it is judged whether or not the absolute value IΔXfn| of thedeviation ΔXfn and the absolute value |ΔXsn| of the deviation ΔXsn areequal to each other, that is, whether or not lΔXfn|=|ΔXsn|. Further,when it is judged at step 202 that |ΔXfn|=IΔXsn|, the routine proceedsto step 203.

FIG. 12 a to FIG. 12 c are views showing the indicator Xfn and theindicator Xsn when the routine proceeds to step 203 of FIG. 11 and thenew indicator Xsn′ after the correction. The indicators Xf1 and Xf2 atthe time of the first valve opening characteristic shown in FIG. 12 aare deviated from the standard value X in opposite directions to eachother by exactly ΔXf1 and ΔXf2. On the other hand, as shown in FIG. 12b, the indicators Xs1 and Xs2 at the time of the second valve openingcharacteristic are also deviated from the standard value X in oppositedirections to each other by exactly ΔXs1 and ΔXs2. Further, thedeviation direction of ΔXs1 and ΔXs2 becomes equal to the deviationdirection of ΔXf1 and ΔXf2 shown in FIG. 12 a. Accordingly, it is judgedYES at step 201. Further, as seen from FIG. 12 a and FIG. 12 b, theabsolute value IΔXf1| of ΔXf1 and the absolute value |ΔXs1| of ΔXs1become equal and, at the same time, the absolute value IΔXf2| of ΔXf2and the absolute value |ΔXs2| of ΔXs2 become equal. Namely,IΔXfn|=IΔXsn| is established, so it is judged YES at step 202. Then,|ΔXfn|=|ΔXsn|stands, therefore, ΔXsn for the new indicator Xsn′ obtainedby the correction at step 106 of FIG. 5 becomes approximately zero asshown in FIG. 12 c. Namely, in this case, before the correction (FIG. 12b), it looks like the deviation ΔXsn exists and variation of the valveopening characteristic exists, but by performing the above correction,it is seen that, in actuality, the deviation ΔXsn does not exist, andaccordingly variation of the valve opening characteristic does not occur(refer to FIG. 12 c).

Referring to FIG. 11 again, when it is judged at step 202 that theabsolute value IΔXfn| of the deviation ΔXfn and the absolute valueIΔXsn| of the deviation ΔXsn are not equal, that is |ΔXfn|≠|ΔXsn|, theroutine proceeds to step 204. FIG. 13 a to FIG. 13 c are views showingthe indicator Xfn and the indicator Xsn when the routine proceeds tostep 204 and the new indicator Xsn′ after the correction. FIG. 13 a issubstantially the same as FIG. 12 a, so the explanation will be omitted.On the other hand, as shown in FIG. 13 b, the indicators Xs1 and Xs2 atthe time of the second valve opening characteristic are also deviatedfrom the standard value X in opposite directions to each other byexactly ΔXs1 and ΔXs2, and the deviation directions of these ΔXs1 andΔXs2 become equal to the deviation directions of ΔXf1 and ΔXf2 shown inFIG. 13 a. Accordingly, it is judged YES at step 201.

As seen from FIG. 13 a and FIG. 13 b, however, the absolute valueIΔXs1|of ΔXs1 becomes larger than the absolute value IΔXf1| of ΔXf1, andalso the absolute value IΔXs2| of ΔXs2 becomes larger than the absolutevalue IΔXf2|of ΔXf2. Namely, in this case, |ΔXfn| becomes not equal toIΔXsn|, and accordingly, it is judged NO at step 202. Then, in thiscase, when the new indicator Xsn′ (=Xsn−(Xfn−Xfr)) is calculated by thecorrection at step 106 of FIG. 5, the new indicator Xsn′ becomes asshown in FIG. 13 c. Namely, the deviation direction of ΔXsn (FIG. 13 c)based on the new indicator Xsn′ after the correction becomes equal tothe deviation direction of ΔXsn (FIG. 13 b) before the correction, andthe absolute value IΔXsn| of ΔXsn after the correction becomes smallerthan the absolute value IΔXsn| of ΔXsn before the correction. Namely, inthis case, the deviation ΔXsn becomes relatively large before thecorrection (FIG. 13 b), accordingly the sum of the variation of thevalve opening characteristic and the variation of the fuel injectionamount looks relatively large, but it is seen that, in actuality, thenew deviation ΔXsn after the correction becomes relatively small.Namely, in this case, it is seen most of the deviation ΔXsn before thecorrection is based on the variation of the fuel injection amount andthat the variation of the valve opening characteristic per se isactually relatively small.

Referring to FIG. 11 again, when it is judged at the above step 201 thatthe positive and negative signs of the deviation ΔXfn and the positiveand negative signs of the deviation ΔXsn are not equal, the routineproceeds to step 205. FIG. 14 a to FIG. 14 c are views showing theindicator Xfn and the indicator Xsn of a certain case when the routinecan proceed to step 205 and the new indicator Xsn′ after the correction.As shown in FIG. 14 a, the indicators Xf1 and Xf2 at the time of thefirst valve opening characteristic are deviated from the standard valueX in opposite directions to each other by exactly ΔXf1 and ΔXf2. On theother hand, in FIG. 14 b, the indicators Xs1 and Xs2 at the time of thesecond valve opening characteristic may not deviate from the standardvalue X or these indicators Xs1 and Xs2 may be slightly deviated inopposite directions to each other with respect to the deviationdirections of ΔXf1 and ΔXf2 in FIG. 14 a. Then, when the correction forthe indicator Xsn at step 106 mentioned above is carried out, the newindicator Xsn′ after the correction becomes as shown in FIG. 14 c.Namely, the amount of variation of the fuel injection amount shown inFIG. 14 a is corrected, therefore new indicators Xs1′ and Xs2′ after thecorrection are deviated from the standard value X by ΔXs1 and ΔXs2.Especially, in this case, as shown in FIG. 14 b, no deviation of theindicator Xsn at the time of the second valve opening characteristicexists at first glance, so seemingly variation of the valve openingcharacteristic does not occur, but it is seen that the variation of theindicator Xsn, that is, the variation of the valve openingcharacteristic, actually occurred by performing the above correction.

Note that, in the above description, the explanation was given by takingas an example the case where the valve opening characteristic waschanged to two different valve opening characteristics (first valveopening characteristic and second valve opening characteristic), but thepresent invention is not limited to this. It is also possible to changethe valve opening characteristic to three or more different valveopening characteristics and detect the variation of the valve openingcharacteristic and the variation of the fuel injection amount based onthe change of the difference of the deviation of the indicator and thestandard value at that time.

In this way, in the present invention, not only the deviation at thetime of the second valve opening characteristic, but also the deviationat the time of the first valve opening characteristic are considered. Inthis way, by calculating the deviation of each cylinder from indicatorsof the state of combustion at two different valve openingcharacteristics and correcting them by using these deviations, itbecomes possible to correctly detect variation among cylinders.Especially, when the real measurement value of the deviation ΔXsn at thetime of the second valve opening characteristic is near zero, there is apossibility that the variation of valve opening characteristics will notbe detected, but in the present invention, in such case as well, itbecomes possible to correctly detect occurrence of a variation of thevalve opening characteristic. Further, naturally, suitable combinationsof several of the above embodiments are also included in the scope ofthe present invention.

FIG. 15 is a lateral sectional view of another spark-ignition internalcombustion engine having a valve opening characteristic control deviceof the present invention mounted thereon. As shown in FIG. 15, intakepassageways of the internal combustion engine 1 are connected to intakemanifolds 71 and 72 arranged at both sides of the intake passageway.Then, passageways of the intake manifold 71 are connected to the firstcylinder #1, the third cylinder #3, and the fifth cylinder #5 arrangedin a line in a left bank BL of the internal combustion engine 1. In thesame way as above, passageways of the intake manifold 72 are connectedto the second cylinder #2, the fourth cylinder #4, and the sixthcylinder #6 arranged in a line in a right bank BR of the internalcombustion engine 1. That is, in the present invention, the odd number(uneven numbers, UN) cylinders are arranged at the left bank BL and, atthe same time, the even number (EN) cylinders are arranged at the rightbank BR. Note that, in FIG. 15, three cylinders are arranged in eachbank, but the number of cylinders in the banks BL and BR may bedifferent as well.

FIG. 16 is a vertical sectional view seen from the front surface of theinternal combustion engine shown in FIG. 15. As seen from FIG. 16, theinternal combustion engine 1 in this case is a so-called V-type internalcombustion engine in which the first cylinder #1 of the left bank BL andthe second cylinder #2 of the right bank BR form a V-shape. Further, asshown in FIG. 16, a valve opening characteristic control device 57L forsetting the valve opening characteristics of the intake valves of thecylinders #1, #3, and #5 of the left bank BL, and a valve openingcharacteristic control device 57R for setting the valve openingcharacteristics of the intake valves of the cylinders #2, #4, and #6 ofthe right bank BR are provided in the internal combustion engine 1.Here, the valve opening characteristic control devices 57L and 57R arethe same as the valve opening characteristic control device 57 explainedby referring to FIG. 3 and FIG. 4, so their explanations will beomitted.

Below, an explanation will be given of the detection of variation amongbanks in such a V-type internal combustion engine. FIG. 17 is a view ofa flowchart of a program for the operation of the variation detectiondevice of the internal combustion engine shown in FIG. 15 and FIG. 16.In the case of the normal operation where the intake amount becomesconstant, the program 300 shown in FIG. 17 is executed by the ECU 27 atthe time of the idling after for example warmup. In the program 300shown in FIG. 17, step 301 to step 308 are the same as steps 101 to 108of FIG. 5, so their explanations will be omitted. The deviation ΔXsncalculated at step 308 includes the deviation ΔXs1 for the firstcylinder #1, the deviation ΔXs2 for the second cylinder #2, thedeviation ΔXs3 for the first cylinder #3, the deviation ΔXs4 for thefirst cylinder #4, the deviation ΔXs5 for the first cylinder #5, and thedeviation ΔXs6 for the first cylinder #6. Further, at step 309, thesedeviations are averaged for each bank. Namely, at step 309, the averagevalue avgΔXsn (UN) of the deviations ΔXs1, ΔXs3, and ΔXs5 for the leftbank BL, that is, the odd number (UN) deviations ΔXsn(UN), is calculatedand, at the same time, the average value avgΔXsn (EN) of deviationsΔXs2, ΔXs4, and ΔXs6 for the right bank BR, that is, the even number(EN) deviations ΔXsn(EN), is calculated. Then, the average valueavgΔXsn(UN) is made the deviation ΔXsL for the left bank BL and, at thesame time, the average value avgΔXsn(EN) is made the deviation ΔXsR forthe right bank BR.

An explanation will be given of the situation of finding such deviationΔXsL and deviation ΔXsR by referring to FIG. 18 a and FIG. 18 b. Theordinates in FIG. 18 a and FIG. 18 b indicate the indicator Xsn at thetime of the second valve opening characteristic. Here the indicator Xsn′after the correction calculated at step 306 is shown. The abscissa inFIG. 18 a indicates the first cylinder #1 to the sixth cylinder #6 ofthe internal combustion engine shown in FIG. 15 etc. Further, theabscissa in FIG. 18 b indicates the left bank BL and the right bank BR.Note that, the dotted lines X shown in these figures indicate thestandard value the same as the case of FIG. 9 etc.

Assume that deviations ΔXsn calculated at step 308 of FIG. 17, that is,the deviation ΔXs1 to the deviation ΔXs6, are distributed as shown infor example FIG. 18 a. That is, as seen from FIG. 18 a, the deviationsΔXs1, ΔXs3, and ΔXs5 of the cylinders of the left bank BL aredistributed so as to be generally higher than the standard value X.Contrary to this, the deviations ΔXs2, ΔXs4, and ΔXs6 of the cylindersof the right bank BR are distributed so as to be generally lower thanthe standard value X. Then, at step 309 of FIG. 17, when the deviationΔXsL at the left bank BL and the deviation ΔXsR at the right bank BR arecalculated by averaging the deviations in each bank, the positions ofthe deviation ΔXsL and the deviation ΔXsR are determined as shown inFIG. 18 b. In this way, by averaging the deviations ΔXsn of thecylinders in each bank, the deviation ΔXsL and the deviation ΔXsR foreach bank are found. As mentioned above, the deviation ΔXsn representsthe variation of the valve opening characteristic of the intake valve 9,therefore, by calculating the deviation ΔXsL and the deviation ΔXsR foreach bank, it becomes possible to judge the tendency of variation of thevalve opening characteristic in each bank. That is, in the case shown inFIG. 18 b, the variation of the valve opening characteristic at the leftbank BL tends to be larger than the standard value X, and the variationof the valve opening characteristic at the right bank BR tends to besmaller than the standard value X. Especially, where the number ofcylinders in each bank is large, it is not necessary to judge thevariation of the valve opening characteristic for each cylinder,therefore it is advantageous to find the variation of the valve openingcharacteristic between banks.

Note that, in the program 300 of FIG. 17, after calculating thedeviations ΔXsn at step 308, these deviations ΔXsn are averaged for eachbank at step 309, but it is also possible to employ another method offinding the deviations ΔXsL and ΔXsR without finding the average. Forexample, it is also possible to calculate only the deviation concerningone cylinder among three cylinders at the left bank BL, for example, thethird cylinder #3 located at the center of the bank and use thedeviation ΔXs3 as the deviation ΔXsL at the left bank BL. Further, it isalso possible to employ for example the value in the middle amongdeviations ΔXs1, ΔXs3, and ΔXs5 of the left bank BL (for example thedeviation ΔXs3 in the case of ΔXs1<ΔXs3<ΔXs5) as the deviation ΔXsL forthe left bank BL without finding the average. It is also possible todetermine the deviation ΔXsR without finding the average in the same wayas the above also for the right bank BR.

It is also possible to calculate the deviation ΔXsL at the left bank BLand the deviation ΔXsR at the right bank BR by a method other than theprogram 300 shown in FIG. 17. Both of FIG. 19 and FIG. 20 are viewsshowing flowcharts of other programs for the operation of the variationdetection device among banks of the internal combustion engine shown inFIG. 15 and FIG. 16. Program 500 shown in FIG. 19 and FIG. 20 isexecuted by the ECU 27 at the time of idling after for example warmup inthe case of normal operation where the intake amount becomes constant.Below, an explanation will be given of other calculation methods forcalculating the deviation ΔXsL and the deviation ΔXsR by referring toFIG. 19 and FIG. 20.

At step 501 a of FIG. 19, in the same way as the case of the program100, the indicator Xfn of the state of combustion in the first valveopening characteristic is detected for each cylinder. In this case, theinternal combustion engine 1 shown in FIG. 15 includes six cylinders,that is, the first cylinder #1 to the sixth cylinder #6, therefore, theindicator Xf1 to the indicator Xf6 will be detected. Note that, in thisfirst valve opening characteristic, the case where the operating angleand/or the amount of lift is relatively large and the case where thevariation of the valve opening characteristic is small enough to ignoreis selected. Accordingly, at the time of the first valve openingcharacteristic, the intake amount becomes relatively large. Note that,the case of an embodiment controlling only one of the operating angleand amount of lift by the valve opening characteristic control device isthe case where the operating angle or amount of lift is relativelylarge. Further, indicators of the state of combustion at step 501 andstep 504 mentioned later are the same as the case referring to FIG. 6 a,FIG. 6 b, FIG. 7 a, and FIG. 7 b, so the explanation will be omitted.

Next, the routine proceeds to step 501 b, where the indicator Xf1 to theindicator Xf6 for the first cylinder #1 to the sixth cylinder #6 areaveraged for the banks. As mentioned above, the first cylinder #1, thethird cylinder #3, and the fifth cylinder #5 are arranged at the leftbank BL, and the second cylinder #2, the fourth cylinder #4, and thesixth cylinder #6 are arranged at the right bank BR. Accordingly, atstep 501 b, first the average value avgXfn(UN) of the indicators Xf1,Xf3, and Xf5 for the left bank BL, that is the indicators Xfn(UN) of theodd number (UN) cylinders, is calculated and made the indicator XfL forthe left bank BL. In the same way as above, the average value avgXfn(EN)of the indicators Xf2, Xf4, and Xf6 for the right bank BR, that is, theindicators Xfn(EN) of the even number (EN) cylinders, is calculated andmade the indicator XfR for the right bank BR.

Note that after detecting the indicators Xfn at step 501 a, theseindicators Xfn are averaged for each bank at step 501 b, but in theprogram 500 as well, another method of finding the indicators XfL andXfR without finding the average can be employed as well. For example, itis also possible to detect only the indicator of the state of combustionfor any one cylinder among the three cylinders at the left bank BL, forexample, the third cylinder #3 located at the center of the bank, anduse this as the indicator XfL of the state of combustion of the leftbank BL. Further, it is also possible to employ for example the middlevalue among the indicators Xf1, Xf3, and Xf5 of the left bank BL as theindicator XfL for the left bank BL without finding the average. The sameis true also for the right bank BR.

When the indicator XfL for the left bank BL and the indicator XfR forthe right bank BR are calculated, the routine proceeds to step 502. Atstep 502, the absolute values of differences between the indicators XfLand XfR obtained at step 501 and standard values XfrL and XfrRpreviously determined for these indicators (in more detail, themagnitude of the difference from the previously determined standardvalue) is calculated, and it is judged whether or not the absolutevalues of these differences are larger than a predetermined value D1.These standard values XfrL and XfrR are the normal values or targetvalues in the drive states for indicators of the state of combustion.They are found in advance by experiments etc., formed into maps, andstored in the ECU 27. Namely, for example, the system is configured sothat the standard values XfrL and XfrR of indicators of the state ofcombustion at that time are obtained from for example the engine speedand the opening degree of the accelerator. Further, the predeterminedvalue D1 in the above step 502 is a value larger than zero. In the ECU27, where it is judged that at least one of the absolute values(|XfL−XfrL|, |XfR−XfrR|) of the differences between the indicators XfLand XfR and standard values XfrL and XfrR is larger than thepredetermined value D1, the routine proceeds to step 503, while when itis judged that the absolute values (|Xfn−XfrL|, |XfL−XfrR|) of thesedifferences are not larger than the predetermined value D1, the routineproceeds to step 504 a. Note that, it is also possible if thepredetermined standard values XfrL and XfrR are the average values Xfavg(=ΣXfn/n) from the indicators Xf1 to Xf6.

At step 503, the differences ΔXfL and ΔXfR between the above indicatorsXfL and XfR obtained at step 501 b and the standard values XfrL and XfrRpreviously determined for the indicators (in more detail, magnitudes ofdifferences from previously determined standard values) (that is,ΔXfL=XfL−XfrL, ΔXfR=XfR−XfrR) are calculated for each bank. Thesestandard values XfrL and XfrR are normal values or target values indrive states for indicators of the state of combustion. They are foundin advance by experiments etc., formed into maps, and stored in the ECU27. Namely, the system is configured so that the standard values XfrLand XfrR of indicators of the state of combustion at that time can beobtained from for example the engine speed and the opening degree of theaccelerator. By step 503, the differences ΔXfL and ΔXfR between theindicators XfL and XfR of the state of combustion of the banks (leftbank BL and right bank BR) and the standard values XfrL and XfrR (thatis, deviations for each bank) are obtained. The indicators XfL and XfRat the time of the first valve opening characteristic represent theinfluence of the variation of the fuel injection amount in the same wayas above Xfn, therefore, by calculating the deviations ΔXfL and ΔXfRfrom the standard values XfrL and XfrR, the variation of the fuelinjection amount is learned.

In the present embodiment, in FIG. 6 a to FIG. 7 b, the value at thetime of normal operation, for example, XA0, corresponds to the standardvalues XfrL and XfrR. Further, the difference, for example ΔXA1 betweenthis XA0 and the value in each bank, for example XA1, is calculated asthe deviations ΔXfL and ΔXfR. Accordingly, ΔXA1 and ΔXA2 in FIG. 6 a cancorrespond to deviations ΔXfL and ΔXfR at step 503. In the same way asthe above, ΔXB1 and ΔXB2 in FIG. 6 b, ΔXC1 and ΔXC2 in FIG. 7 a, andΔXD1 and ΔXD2 in FIG. 7 b can correspond to the deviations ΔXfL andΔXfR.

Next, at step 504 a, the indicator Xsn of the state of combustion whenthe valve opening characteristic is made the second valve openingcharacteristic is detected for each cylinder. In this case, the internalcombustion engine 1 shown in FIG. 15 includes six cylinders, that is,the first cylinder #1 to the sixth cylinder #6, therefore, the indicatorXs1 to the indicator Xs6 are detected. In the control by the presentcontrol routine as well, at this second valve opening characteristic,the operating angle and/or amount of lift is made smaller than that atthe time of the first valve opening characteristic. Accordingly, at thetime of the second valve opening characteristic, the intake amountbecomes relatively small. Note that, in the case of an embodimentcontrolling only one of the operating angle and the amount of lift bythe valve opening characteristic control device, the operating angle orthe amount of lift is made smaller than that at the time of the firstvalve opening characteristic.

Further, at step 504 a, the intake amount, the rotation speed, and theengine load when the valve opening characteristic is made the secondvalve opening characteristic are made the same as those when the valveopening characteristic was the first valve opening characteristic atstep 501. Namely, if the valve opening characteristic control devices57L and 57R normally operate, the throttle valve 56 is controlled sothat the intake amount becomes the same at the time of each valveopening characteristic. Note that, naturally, the indicator Xsn of thestate of combustion detected at step 504 a is made the same type as theindicator Xfn of the state of combustion detected at step 501.

Next, the routine proceeds to step 504 b, where the indicator Xs1 to theindicator Xs6 for the first cylinder #1 to the sixth cylinder #6 areaveraged for each bank. As mentioned above, the first cylinder #1, thethird cylinder #3, and the fifth cylinder #5 are arranged at the leftbank BL, and the second cylinder #2, the fourth cylinder #4, and thesixth cylinder #6 are arranged at the right bank BR. Accordingly, atstep 504 b, the average value avgXsn(UN) of the indicators Xs1, Xs3, andXs5 for the left bank BL, that is the indicators Xsn(UN) of the oddnumber (UN) cylinders, is calculated, and this average value is made theindicator XsL for the left bank BL. In the same way as the above, theaverage value avgXsn(EN) of the indicators Xs2, Xs4, and Xs6 for theright bank BR, that is, the indicators Xsn(EN) of the even number (EN)cylinders, is calculated, and this average value is made the indicatorXsR for the right bank BR.

Note that, for the indicators XfL and XfR, in the same way as the abovecase, it is also possible to find the indicators XsL and XsR withoutfinding the average.

When the indicators XsL and XsR in the state of combustion at the secondvalve opening characteristic are detected for each bank at step 504 b,the routine proceeds to step 505. At step 505, the differences(XfL−XfrL, XfR−XfrR) between the indicators XfL and XfR and the standardvalues XfrL and XfrR are found and it is judged whether or not theabsolute values |XfL−XfrL| and |XfR−XfrR| of these differences arelarger than a predetermined value D1′. The predetermined value D1′ atstep 505 is a value larger than zero. In the same way as the case of thepredetermined value D1 mentioned above, the predetermined value D1′ isstored in the ECU 27 in the form of a map as a function of the load Land engine speed N. Note that, when the routine passes step 503, it isalso possible to directly use the absolute values of the deviations ΔXfLand ΔXfR. When it is judged at step 505 that at least one of theabsolute values |XfL−XfrL| and |XfR−XfrR| is larger than thepredetermined value D1′, the routine proceeds to step 506, while when itis judged that the absolute values |XfL−XfrL| and |XfR−XfrR| are notlarger than the predetermined value D1′, the routine proceeds to step507.

Here, an explanation will be given of the judgment at step 505 describedabove. When there is variation in the valve opening characteristiccontrol devices 57L and 57R, that is, when there is variation in thevalve opening characteristics, a difference arises in the intake amountbetween the banks. It is learned that the smaller the operating angleand amount of lift, the larger the influence. On the other hand, thelarger the operating angle and amount of lift, the smaller the influenceupon the indicators due to the variation of the valve openingcharacteristics. Further, when the operating angle and amount of liftare certain extents of values or more, it can be considered that theinfluence of the variation of the valve opening characteristics issubstantially ignorable. For this reason, when the operating angle andamount of lift are relatively large, that is, when the influence withrespect to the indicators mentioned above is detected at the time of thefirst valve opening characteristic, it can be decided that this cause isnot variation of the valve opening characteristic control devices 57Land 57R, but a portion other than the valve opening characteristiccontrol devices 57L and 57R, i.e., in the present invention, thevariation of the fuel injection amount by the fuel injection system.Namely, when the absolute values |XfL−XfrL| and |XfR−XfrR| ofdifferences (XfL−XfrL, XfR−XfrR) between the indicators XfL and XfR andstandard values XfrL and XfrR are larger than the predetermined valueD1′ as at step 505, it can be judged that variation of the fuelinjection amount occurs. On the other hand, when the operating angle andthe amount of lift are relatively small, that is, where the influencewith respect to the indicators mentioned above occurs at the time of thesecond valve opening characteristic, this cause is not only variation ofthe valve opening characteristic by the valve opening characteristiccontrol devices 57L and 57R, but also the mixing of variation of thefuel injection amount by the fuel injection system which is a portionother than the valve opening characteristic control devices 57L and 57R.

Further, when at least one of the absolute values |XfL−XfrL| and|XfR−XfrR| of the differences (XfL−XfrL, XfR−XfrR) between theindicators XfL and XfR and their standard values XfrL and XfrR is largerthan the predetermined value D1′, the routine proceeds to step 506. Atstep 506, by subtracting the difference (XfL−XfrL) between the indicatorXfL and the standard value XfrL from the indicator XsL for the left bankBL at the time of the second valve opening characteristic calculated atstep 504 b, a new indicator XsL′ (=XsL−(XfL−XfrL)) for the second valveopening characteristic is calculated. In the same way as the above, bysubtracting the difference (XfR−XfrR) between the indicator XfR and thestandard value XfrR from the indicator XsR for the right bank BR, a newindicator XsR′ (=XsR−(XfR−XfrR)) for the second valve openingcharacteristic is calculated. Here, the difference (XfL−XfrL) and thedifference (XfR−XfrR) are not absolute values, but in states includingthe positive and negative signs as they are. Accordingly, when thedifference (XfL−XfrL) and the difference (XfR−XfrR) are positive values,the new indicators XsL′ and XsR′ become smaller than the originalindicators XsL and XsR, while when the difference (XfL−XfrL) and thedifference (XfR−XfrR) are negative values, the new indicators XsL′ andXsR′ become larger than the original indicators XsL and XsR. In thisway, by correcting the amounts of variation of the fuel injectionamounts (XfL−XfrL=ΔXfL and XfR−XfrR=ΔXfR), new indicators XsL′ and XsR′not including the influence of variation of the fuel injection amountcan be calculated. Accordingly, the new indicator XsL′ represents theinfluence of only the variation of the valve opening characteristic atthe left bank BL, and the new indicator XsR′ represents the influence ofonly the variation of the valve opening characteristic at the right bankBR.

Next, at step 507, the absolute values of the differences between theindicators XsL and XsR obtained at step 504 b or the new indicators XsL′and XsR′ obtained at step 506 and the standard values XsrL and XsrRpreviously determined for these indicators (in more detail, magnitudesof differences from the previously determined standard values) arecalculated. Namely, when the new indicators XsL′ and XsR′ are notcalculated (where it is judged NO at step 505), the absolute values(|XsL−XsrL|, |XsR−XsrR|) of differences between the indicators XsL andXsR and their standard values XsL and XsR are calculated. Further, whenthe new indicators XsL′ and XsR′ for the banks are calculated at step506, the absolute values (|XsL′−XsrL|, |XsR′−XsrR|) of differencesbetween the indicators XsL′ and XsR′ and their standard values XsrL andXsrR are calculated. These standard values XsrL and XsrR are normalvalues or target values for indicators in drive states in the same wayas the standard values XfrL and XfrR. Further, it is judged at step 507whether or not the absolute values (|XsL−XsrL| or |XsL′−XsrL| and|XsR−XsrR| or |XsR′−XsrR−) of these differences are larger than apredetermined value D2. The predetermined value D2 at step 507 is avalue larger than zero. The predetermined value D2 is stored in the ECU27 in the form of a map as a function of the load L and the engine speedN. At step 507, when it is judged that an absolute value (|XsL−XsrL| or|XsL′−XsrL| and |XsR−XsrR| or |XsR′−XsrR|) of differences is larger thanthe predetermined value D2, the routine proceeds to step 508. On theother hand, when it is judged at step 507 that the absolute values ofthe differences mentioned above are not larger than the predeterminedvalue, it is judged that variation of valve opening characteristic doesnot exist, and the processing is ended. Note that, it is also possibleif the predetermined standard values XsrL and XsrR are the averagevalues Xsavg (=ΣXsn/n) of the indicator Xs1 to Xs6.

At step 508, the differences ΔXsL (=XsL−XsrL or =XsL′−XsrL) andΔXsR(=XsR−XsrR or =XsR′−XsrR) between the indicators XsL and XsRobtained at step 504 b or new indicators XsL′ and XsR′ obtained at step506 and the standard values XsrL and XsrR previously determined forthese indicators (in more detail, magnitudes of differences from thepreviously determined standard values) are calculated for each bank.These standard values XsrL and XsrR are normal values or target valuesfor the indicators in the drive states in the same way as the abovestandard values XfrL and XsrR. For example, when the relationship shownin FIG. 6 a for the time of the second valve opening characteristicdifferent from the case of the first valve opening characteristicmentioned above is obtained, the value at the time of normal operation,for example, XA0, corresponds to the standard values XsrL and XsrR.Then, the difference, for example ΔXA1 between this XA0 and the value ineach cylinder, for example XA1 is calculated as the deviations ΔXsL andΔXsR. Accordingly, in this case, ΔXA1 and ΔXA2 in FIG. 6 a cancorrespond to the deviations ΔXsL and ΔXsR at step 508. In the same wayas the above case, ΔXB1 and ΔXB2 in FIG. 6 b, ΔXC1 and ΔXC2 in FIG. 7 a,and ΔXD1 and ΔXD2 in FIG. 7 b can correspond to the deviations ΔXsL andΔXsR. By step 508, the differences ΔXsL and ΔXsR between the indicatorsXsL and XsR of the state of combustion in the banks or new indicatorsXsL′ and XsR′ and the standard values XsrL and XsrR are obtained, andthe processing is ended. As mentioned above, in the indicators XsL andXsR at the time of the second valve opening characteristic, thevariation of the fuel injection amount and the variation of the valveopening characteristic may be mixed, but in the present invention, whenvariation of the fuel injection amount exists, this is corrected (thedifference (XfL−XfrL) is subtracted from the indicators XsL and XsL′and, at the same time, the difference (XfR−XfrR) is subtracted from theindicators XsR and XsR′), therefore, by calculating the deviations ΔXsLand ΔXsR, just the variation of the valve opening characteristic can becalculated.

In this way, in the present invention, not only the deviation at thetime of the second valve opening characteristic, but also the deviationat the time of the first valve opening characteristic are considered. Inthis way, by calculating the deviation in each bank from the indicatorsof the state of combustion at two different valve openingcharacteristics and performing correction by using these deviations, itbecomes possible to correctly detect the inter-bank variation.Especially, when the real measurement value of the deviation ΔXsn at thetime of the second valve opening characteristic is near zero, there wasthe possibility that the variation of the valve opening characteristicwas not detected, but in the present invention, even in such case, itbecomes possible to correctly detect existence of variation of the valveopening characteristic.

Note that, after the deviation ΔXsL at the left bank BL and thedeviation ΔXsR at the right bank BR are calculated, preferably the valveopening characteristic control device 57L and the valve openingcharacteristic control device 57R for each bank (refer to FIG. 16) areadjusted so that these deviation ΔXsL and deviation ΔXsR are eliminated.

FIG. 21 is a view of a flowchart of a program for the operationperformed for eliminating the variation among banks in the case of theinternal combustion engine shown in FIG. 15 and FIG. 16. Below, anexplanation will be given of the elimination of the deviation ΔXsL andthe deviation ΔXsR for the variation of the valve opening characteristicamong banks by adjusting the valve opening characteristic controldevices 57L and 57R by referring to FIG. 21. At step 601 of the program600 shown in FIG. 21, both of the deviation ΔXsL of the left bank BL andthe deviation ΔXsR of the right bank BR are acquired. Assume that thesedeviation ΔXsL and deviation ΔXsR are obtained from either of step 309of the program 300 shown in FIG. 17 or step 508 of the program 500 shownin FIG. 19 and FIG. 20 and stored in the ECU 27. Accordingly, at step601, these deviations ΔXsL and ΔXsR are acquired from the ECU 27.

Next, at step 602, it is judged whether or not the deviation ΔXsL islarger than the predetermined value ΔXsL0 and whether or not thedeviation ΔXsR is larger than the predetermined value ΔXsR0. Assume thatthe predetermined values ΔXsL0 and ΔXsR0 are values previouslydetermined by experiments etc. and near zero and are previously storedin the ROM or RAM of the ECU 27. When the deviation ΔXsL is not largerthan the predetermined value ΔXsL0 and the deviation ΔXsR is not largerthan the predetermined value ΔXsR0, it is decided that variation of thevalve opening characteristic slightly exists, but to an ignorable extentand the processing is ended. On the other hand, when the deviation ΔXsLis larger than the predetermined value ΔXsL0 and/or the deviation ΔXsRis larger than the predetermined ΔXsR0, the routine proceeds to step603. At step 603, it is judged whether or not the deviation ΔXsL of theleft bank BL is larger than the deviation ΔXsR of the right bank BR.When the deviation ΔXsL is larger than the deviation ΔXsR, the routineproceeds to step 604, while when the deviation ΔXsL is smaller than thedeviation ΔXsR, the routine proceeds to step 605.

At step 604, by subtracting a predetermined value α from the targetvalve opening characteristic correction learning value VL of the valveopening characteristic control device 57L for the intake valve 9 of acylinder at the left bank BL, a new target valve opening characteristiccorrection learning value VL is obtained. Then, by adding apredetermined value β to the target valve opening characteristiccorrection learning value VR of the valve opening characteristic controldevice 57R for the intake valve of a cylinder at the right bank BR, anew target valve opening characteristic correction learning value VR isobtained. Assume that the predetermined values α and β are small valueslarger than zero and stored in the ECU 27 in advance. Thesepredetermined values α and β may be values equal to each other too.

On the other hand, when the routine proceeds to step 605, conversely tothe case of step 604, by adding the predetermined value α to the targetvalve opening characteristic correction learning value VL of the valveopening characteristic control device 57L at the left bank BL, the newtarget valve opening characteristic correction learning value VL isobtained. Further, by subtracting the predetermined value β from thetarget valve opening characteristic correction learning value VR of thevalve opening characteristic control device 57R at the right bank BR, anew target valve opening characteristic correction learning value VR isobtained.

Note that the predetermined values α and β at step 604 and step 605 arevalues giving differences (VL−α, VR−β) between the target valve openingcharacteristic correction learning values VL and VR and thesepredetermined values of zero or more.

Next, at step 606, the new target valve opening characteristiccorrection learning value VL obtained at step 604 or step 605 is addedto the previously determined base target value VL0, and the result ismade the new valve opening characteristic target value for the valveopening characteristic control device 57L of the left bank BL. For theright bank BR as well, in the same way as the above, the new targetvalve opening characteristic correction learning value VR obtained atstep 604 or step 605 is added to the previously determined base targetvalue VR0, and the result is made the new valve opening characteristictarget value for the valve opening characteristic control device 57R ofthe right bank BR. Then, the routine returns to step 601 again. Thisseries of processing is repeatedly carried out to gradually make thetarget valve opening characteristic correction learning value VL and thetarget valve opening characteristic correction learning value VRapproach equal values. As a result, the deviation ΔXsL of the left bankBL and the deviation ΔXsR of the right bank BR are eliminated, that is,the variation of the valve opening characteristics between the left bankBL and the right bank BR is eliminated. In this way, in the program 600,the valve opening characteristic is changed by exactly the amount of thevariation of valve opening characteristics among cylinders detected soas not to include variation of the fuel injection amount, therefore moreprecise control becomes possible. By that, it becomes possible to avoidany adverse influence upon the drivability of the automobile mountingsuch internal combustion engine and the emission in the exhaust system.

Note that, in the program 600 shown in FIG. 21, by repeatedlysubtracting and/or adding the small values α and β, the deviation ΔXsLand the deviation ΔXsR are eliminated. At step 604 and step 605,however, it is also possible to use the value of half of the differencebetween the deviation ΔXsL and the deviation ΔXsR (=(ΔXsL-ΔXsR)/2) asthe predetermined values α and β. In this case, more than the case wherethe processing is repeatedly carried out by using the small values α andβ, the target valve opening characteristic correction learning value VLand the target valve opening characteristic correction learning value VRare directly made equal, so it becomes possible to shorten the timerequired for eliminating the inter-bank variation.

The first cylinder #1 to the fourth cylinder #4 included in the internalcombustion engine 1 shown in FIG. 1 and FIG. 2 are controlled in theirvalve opening characteristics by a single common valve openingcharacteristic control device 57, but sometimes an internal combustionengine is provided with a plurality of valve opening characteristiccontrol devices 57 corresponding to the plurality of cylinders so thatthe valve opening characteristics for the intake valves of the cylinderscan be individually controlled. In such internal combustion engine (notillustrated) as well, it is possible to perform the same control as thatof the program 600 shown in FIG. 21.

Below, an explanation will be given of the control in for example afour-cylinder internal combustion engine provided with a valve openingcharacteristic control device for each cylinder. This not illustratedinternal combustion engine is provided with four valve openingcharacteristic control devices 57(#1) to 57(#4) (not illustrated). Thesevalve opening characteristic control devices 57(#1) to 57(#4) cancontrol the valve opening characteristics of the first cylinder #1 tothe fourth cylinder #4, respectively (all not illustrated). FIG. 22 is aview of a flowchart of the program for the operation performed foreliminating the inter-cylinder variation in the case of a four-cylinderinternal combustion engine provided with a valve opening characteristiccontrol device for each cylinder. In the program 700 shown in FIG. 22,the control for two cylinders among the four cylinders, i.e., the firstcylinder #1 and the second cylinder #2, is carried out.

At step 701 of the program 700 shown in FIG. 22, the deviation ΔXs1 forthe first cylinder #1 and the deviation ΔXs2 for the second cylinder #2are acquired. These deviations ΔXs1 and ΔXs2 are found from step 108 ofthe program 100 shown in FIG. 5.

Then, at step 702, it is judged whether or not the deviation ΔXs1 islarger than a predetermined value ΔXs10 and whether or not the deviationΔXs2 is larger than a predetermined value ΔXs20. Assume that thepredetermined values ΔXs10 and ΔXs20 are values previously determined byexperiments etc. and near zero and were previously stored in the ROM orRAM of the ECU 27. When the deviation ΔXs1 is not larger than thepredetermined value ΔXs10 and the deviation ΔXs2 is not larger than thepredetermined value ΔXs20, it is decided that slight variation of thevalve opening characteristic exists, but to an ignorable extent, and theprocessing is ended. On the other hand, when the deviation ΔXs1 islarger than the predetermined value ΔXs10 and/or the deviation ΔXs2 islarger than the predetermined value ΔXs20, the routine proceeds to step703. At step 703, it is judged whether or not the deviation ΔXs1 of thefirst cylinder #1 is larger than the deviation ΔXs2 of the secondcylinder #2. When the deviation ΔXs1 is larger than the deviation ΔXs2,the routine proceeds to step 704, while when the deviation ΔXs1 issmaller than the deviation ΔXs2, the routine proceeds to step 705.

At step 704, by subtracting a predetermined value a from the targetvalve opening characteristic correction learning value V1 of the valveopening characteristic control device 57 (#1) for the intake valve 9 ofthe first cylinder #1, a new target valve opening characteristiccorrection learning value V1 is obtained. Then, by adding apredetermined value β to the target valve opening characteristiccorrection learning value V2 of the valve opening characteristic controldevice 57 (#2) for the intake valve of the first cylinder #2, a newtarget valve opening characteristic correction learning value V2 isobtained. Assume that the predetermined values α and β are small valueslarger than zero and were previously stored in the ECU 27. Thesepredetermined values α and β may be values equal to each other as well.

On the other hand, when the routine proceeds to step 705, conversely tothe case of step 704, by adding the predetermined value α to the targetvalve opening characteristic correction learning value V1 of the valveopening characteristic control device 57 (#1) in the first cylinder #1,a new target valve opening characteristic correction learning value V1is obtained. Then, by subtracting the predetermined value β from thetarget valve opening characteristic correction learning value V2 of thevalve opening characteristic control device 57 (#2) in the secondcylinder #2, a new target valve opening characteristic correctionlearning value V2 is obtained.

Note that the predetermined values α and β at step 704 and step 705 arevalues giving differences (V1−α, V2−β) between the target valve openingcharacteristic correction learning values V1 and V2 and thesepredetermined values α and β of zero or more.

Next, at step 706, the new target valve opening characteristiccorrection learning value V1 obtained at step 704 or step 705 is addedto the previously determined base target value V10, and the result ismade the new valve opening characteristic target value for the valveopening characteristic control device 57 (#1) of the first cylinder #1.For the second cylinder #2 as well, in the same way as the above, thenew target valve opening characteristic correction learning value V2obtained at step 704 or step 705 is added to the previously determinedbase target value V20, and the result is made the new valve openingcharacteristic target value for the valve opening characteristic controldevice 57 (#2) of the second cylinder #2. Then, the routine returns tostep 701 again. By repeatedly performing this series of processing, thetarget valve opening characteristic correction learning value V1 and thetarget valve opening characteristic correction learning value v2gradually approach equal values. As a result, the deviation ΔXs1 of thefirst cylinder #1 and the deviation ΔXs2 of the second cylinder #2 areeliminated, that is, the variation of the valve opening characteristicbetween the first cylinder #1 and the second cylinder #2 is eliminated.Then, the same processing as that of the program 700 is carried out forthe deviation ΔXs1 of the first cylinder #1 and the deviation ΔXs3 ofthe third cylinder. Then, the same processing as that of the program 700is carried out also for the deviation ΔXs1 of the first cylinder #1 andthe deviation ΔXs4 of the fourth cylinder #4. By this, the variation ofvalve opening characteristics among all cylinders of the internalcombustion engine can be eliminated. In this way, in the program 700,the valve opening characteristic is changed by exactly the amount of thevariation of the valve opening characteristic among cylinders detectedso as not to include the variation of the fuel injection amount,therefore more precise control becomes possible. By that, it becomespossible to avoid any adverse influence upon the drivability of theautomobile mounting such an internal combustion engine and the emissionin the exhaust system.

Further, naturally, at step 704 and step 705, as the predeterminedvalues α and β, it is also possible to use a value of half of thedifference between the deviation ΔXs1 and the deviation ΔXs2(=(ΔXs1−ΔXs2)/2).

Note that, in the present invention, the detailed explanation was givenbased on the specific embodiments, but a person skilled in the art canmake various changes and corrections without deviation from the scopeand concept of the present invention. Further, appropriate combinationsof several of embodiments mentioned above are included in the scope ofthe present invention.

1-16. (canceled)
 17. An inter-cylinder variation detection device of an internal combustion engine comprising: a valve opening characteristic setting means for changing an operating angle and/or amount of lift of an intake valve, wherein the valve opening characteristic setting means can set a first valve opening characteristic and a second valve opening characteristic having a smaller operating angle or amount of lift than that at the time of the first valve opening characteristic, and further a calculating means for detecting an indicator of the state of combustion in each cylinder at the time of the first valve opening characteristic and the time of the second valve opening characteristic set by said valve opening characteristic setting means and, at the same time, calculating the deviation between these indicators and a standard value for each cylinder and a detecting means for detecting the variation among cylinders by using the deviation for each cylinder at the time of the first valve opening characteristic and the deviation for each cylinder at the time of the second valve opening characteristic calculated by said calculating means.
 18. An inter-cylinder variation detection device of an internal combustion engine comprising: a valve opening characteristic setting means for changing an operating angle or amount of lift of an intake valve, wherein the valve opening characteristic setting means can set a first valve opening characteristic and a second valve opening characteristic having a smaller operating angle or amount of lift than that at the time of the first valve opening characteristic, and further a calculating means for detecting an indicator of the state of combustion in each cylinder at the time of the first valve opening characteristic and the time of the second valve opening characteristic set by said valve opening characteristic setting means and, at the same time, calculating the deviation between these indicators and an average value of the indicators of the state of combustion for the cylinders and a detecting means for detecting the variation among cylinders by using the deviation for each cylinder at the time of the first valve opening characteristic and the deviation for each cylinder at the time of the second valve opening characteristic calculated by said calculating means.
 19. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 17, wherein the variation of the fuel injection amount is detected by the deviation for each cylinder at the time of the first valve opening characteristic set by said valve opening characteristic setting means, and the variation of the valve opening characteristic is detected by the deviation for each cylinder at the time of said second valve opening characteristic.
 20. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 19, wherein when detecting the variation of the valve opening characteristic by the deviation for each cylinder at the time of the second valve opening characteristic set by said valve opening characteristic setting means, the amount of variation of the fuel injection amount for each cylinder detected at the time of the first valve opening characteristic is corrected.
 21. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 17, wherein when detecting the variation among cylinders by said detection device, control is performed so that the drive conditions at times of the first and second valve opening characteristics set by said valve opening characteristic setting means become the same.
 22. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 21, wherein said drive conditions are the rotational speed and torque.
 23. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 21, wherein said detection device detects the variation among cylinders in an idling state of the internal combustion engine.
 24. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 17, wherein said indicator of the state of combustion includes at least one of an air/fuel ratio, rotation fluctuation, and combustion pressure of the internal combustion engine.
 25. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 17, wherein the valve opening characteristic of said intake valve is changed so that the variation among cylinders detected by said detecting means is eliminated.
 26. An inter-cylinder variation detection device of an internal combustion engine comprising: a valve opening characteristic setting means for changing a valve opening characteristic of an intake valve; an indicator detecting means for detecting indicators of the state of combustion for each cylinder at the time of a first valve opening characteristic and at the time of a second valve opening characteristic smaller than the first valve opening characteristic set by the valve opening characteristic setting means; a fuel injection amount variation detecting means for detecting the variation of the fuel injection amount for each of the cylinders by using said indicator of the state of combustion detected by said indicator detecting means at the time of said first valve opening characteristic; and a valve opening characteristic variation detecting means for detecting variation of the valve opening characteristic for each of said cylinders by using said indicator of the state of combustion detected by said indicator detecting means at the time of said second valve opening characteristic and the variation of the fuel injection amount detected by said fuel injection amount variation detecting means.
 27. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 26, wherein said valve opening characteristic setting means can change the valve opening characteristic of the intake valve for each cylinder, and the variation of the valve opening characteristic for each of said cylinders detected by said valve opening characteristic variation detecting means is eliminated by the valve opening characteristic of said intake valve for each of said cylinders being changed by said valve opening characteristic setting means.
 28. An inter-cylinder variation detection device of an internal combustion engine as set forth in claim 26, wherein said indicator of the state of combustion includes at least one of the air/fuel ratio, the rotation fluctuation, and the combustion pressure of the internal combustion engine.
 29. An inter-bank variation detection device of an internal combustion engine comprising: a valve opening characteristic setting means for changing a valve opening characteristic of an intake valve for each bank; an indicator detecting means for detecting indicators of the state of combustion for each cylinder at the time of a first valve opening characteristic and at the time of a second valve opening characteristic smaller than the first valve opening characteristic set by the valve opening characteristic setting means; a fuel injection amount variation detecting means for detecting the variation of the fuel injection amount for each of said cylinders by using said indicator of the state of combustion detected by said indicator detecting means at the time of said first valve opening characteristic; and a valve opening characteristic variation detecting means for detecting the variation of the valve opening characteristic for each of said cylinders by using said indicator of the state of combustion detected by said indicator detecting means at the time of said second valve opening characteristic and the variation of the fuel injection amount detected by said fuel injection amount variation detecting means and finding the average of the variations of the valve opening characteristics for the cylinders for each bank to thereby detect the variation of the valve opening characteristic for each bank.
 30. An inter-bank variation detection device of an internal combustion engine provided with: a valve opening characteristic setting means for changing a valve opening characteristic of an intake valve for each bank; an indicator detecting means for detecting indicators of the state of combustion for each bank at the time of a first valve opening characteristic and at the time of a second valve opening characteristic smaller than the first valve opening characteristic set by the valve opening characteristic setting means; a fuel injection amount variation detecting means for detecting the variation of the fuel injection amount for each bank by using said indicator of the state of combustion detected by said indicator detecting means at the time of said first valve opening characteristic; and a valve opening characteristic variation detecting means for detecting the variation of the valve opening characteristic for each bank by using said indicator of the state of combustion detected by said indicator detecting means at the time of said second valve opening characteristic and the variation of the fuel injection amount detected by said fuel injection amount variation detecting means.
 31. An inter-bank variation detection device of an internal combustion engine as set forth in claim 29, wherein the valve opening characteristic of said intake valve for each bank is changed by said valve opening characteristic setting means so that the variation of the valve opening characteristic of each bank detected by said valve opening characteristic variation detecting means is eliminated.
 32. An inter-bank variation detection device of an internal combustion engine as set forth in claim 29, wherein said indicator of the state of combustion includes at least one of the air/fuel ratio, the rotation fluctuation, and the combustion pressure of the internal combustion engine. 